WAEC Further Mathematics 2014 past questions and answers

51 questions. Try each one, then open the answer to check yourself and read the explanation.

Question 1

Indices and Logarithms

If 1/5−y = 25(54 − 2y), find the value of y.

  1. A.4
  2. B.2
  3. C.−4
  4. D.−5
Show the answer and explanation

Answer: B (2)

Explanation

5^y = 5² × 5^(4 − 2y) = 5^(6 − 2y), so y = 6 − 2y and y = 2.

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Question 2

Trigonometry

Simplify (1 − sin θ)(1 + sin θ).

  1. A.sin2θ
  2. B.sec2θ
  3. C.tan2θ
  4. D.cos2θ
Show the answer and explanation

Answer: D (cos2θ)

Explanation

(1 − sin θ)(1 + sin θ) = 1 − sin²θ = cos²θ.

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Question 3

Coordinate Geometry

Given that the lines 3x + 4y + 6 = 0 and 4x − by + 3 = 0 are perpendicular, find the value of b.

  1. A.4
  2. B.3
  3. C.1/3
  4. D.1/4
Show the answer and explanation

Answer: B (3)

Explanation

Gradients are −3/4 and 4/b. Perpendicular: (−3/4)(4/b) = −1, so b = 3.

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Question 4

Binary Operations

Given that x * y = (x + y)/2, x o y = x2/y and (3 * b) o 48 = 1/3, find b, where b > 0.

  1. A.8
  2. B.6
  3. C.5
  4. D.4
Show the answer and explanation

Answer: C (5)

Explanation

3 * b = (3 + b)/2. Then ((3 + b)/2)² ÷ 48 = 1/3, so ((3 + b)/2)² = 16, (3 + b)/2 = 4 and b = 5.

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Question 5

Polynomials

If f(x) = 3x3 + 8x2 + 6x + k, and f(2) = 1, find the value of k.

  1. A.−67
  2. B.−61
  3. C.61
  4. D.67
Show the answer and explanation

Answer: A (−67)

Explanation

f(2) = 24 + 32 + 12 + k = 68 + k = 1, so k = −67.

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Question 6

Indices and Logarithms

If 8x ÷ (1/4)y = 1 and log2 (x − 2y) = 1, find the value of (x − y).

  1. A.5/4
  2. B.3/5
  3. C.1
  4. D.2/3
Show the answer and explanation

Answer: A (5/4)

Explanation

2^(3x) × 2^(2y) = 2⁰ gives 3x + 2y = 0; x − 2y = 2. Adding: 4x = 2, x = ½, y = −¾. x − y = 5/4.

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Question 7

Surds

Simplify (1 + √8)/(3 − √2).

  1. A.7 + √2
  2. B.7 + 7√2
  3. C.1 − 7√2
  4. D.1 + √2
Show the answer and explanation

Answer: D (1 + √2)

Explanation

Multiply top and bottom by 3 + √2: (1 + 2√2)(3 + √2)/7 = (7 + 7√2)/7 = 1 + √2.

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Question 8

Binomial Theorem

Using the binomial expansion (1 + x)6 = 1 + 6x + 15x2 + 20x3 + 15x4 + 6x5 + x6, find, correct to three decimal places, the value of (1.98)6.

  1. A.64.245
  2. B.61.255
  3. C.60.255
  4. D.60.245
Show the answer and explanation

Answer: C (60.255)

Explanation

Put x = 0.98: 1 + 5.88 + 14.406 + 18.824 + 13.836 + 5.424 + 0.886 = 60.255 (to 3 d.p.).

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Question 9

Polynomials

If (x + 2) and (3x − 1) are factors of 6x3 + x2 − 19x + 6, find the third factor.

  1. A.2x − 3
  2. B.3x + 1
  3. C.x − 2
  4. D.3x + 2
Show the answer and explanation

Answer: A (2x − 3)

Explanation

(x + 2)(3x − 1) = 3x² + 5x − 2, and 6x³ + x² − 19x + 6 ÷ (3x² + 5x − 2) = 2x − 3.

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Question 10

Sequences and Series

If 2, (k + 1), 8, … form an exponential sequence (GP), find the values of k.

  1. A.−3 and 5
  2. B.5 and −5
  3. C.3 and −3
  4. D.−5 and 3
Show the answer and explanation

Answer: D (−5 and 3)

Explanation

(k + 1)/2 = 8/(k + 1), so (k + 1)² = 16, k + 1 = ±4 and k = 3 or −5.

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Question 11

Probability

A box contains 5 red and k blue balls. A ball is selected at random from the box. If the probability of selecting a blue ball is 2/3, find the value of k.

  1. A.5
  2. B.6
  3. C.8
  4. D.10
Show the answer and explanation

Answer: D (10)

Explanation

k/(5 + k) = 2/3 gives 3k = 10 + 2k, so k = 10.

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Question 14

Matrices and Determinants

If T = (−2 −5 / 3 8), find T−1, the inverse of T. (Matrices written row by row; / separates the rows.)

  1. A.(−8 −5 / 3 2)
  2. B.(−8 −5 / 3 −2)
  3. C.(−8 −5 / −3 2)
  4. D.(−8 −5 / −3 −2)
Show the answer and explanation

Answer: A ((−8 −5 / 3 2))

Explanation

|T| = −16 + 15 = −1. T⁻¹ = (1/−1)(8 5 / −3 −2) = (−8 −5 / 3 2).

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Question 15

Functions

A function is defined by h: x → 2 − 1/(2x − 3), x ≠ 3/2. Find h−1(x), the inverse of h.

  1. A.h−1(x) = (3x − 4)/(2x − 7), x ≠ 7/2
  2. B.h−1(x) = (3x − 7)/(2x − 4), x ≠ 2
  3. C.h−1(x) = (2x − 7)/(4x − 3), x ≠ 3/4
  4. D.h−1(x) = (4x − 7)/(2x − 4), x ≠ 2
Show the answer and explanation

Answer: B (h−1(x) = (3x − 7)/(2x − 4), x ≠ 2)

Explanation

y = 2 − 1/(2x − 3) = (4x − 7)/(2x − 3). Solve for x: 2xy − 3y = 4x − 7, so x = (3y − 7)/(2y − 4).

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Question 16

Functions

A function is defined by h: x → 2 − 1/(2x − 3), x ≠ 3/2. Find h−1(½).

  1. A.6
  2. B.11/6
  3. C.11/4
  4. D.5/3
Show the answer and explanation

Answer: B (11/6)

Explanation

h⁻¹(½) = (3/2 − 7)/(1 − 4) = (−11/2)/(−3) = 11/6.

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Question 17

Differentiation

The radius of a sphere is increasing at a rate of 3 cm s−1, find the rate of increase in the surface area, when the radius is 2cm.

  1. A.8π cm2s−1
  2. B.16π cm2s−1
  3. C.24π cm2s−1
  4. D.48π cm2s−1
Show the answer and explanation

Answer: D (48π cm2s−1)

Explanation

A = 4πr², dA/dt = 8πr × dr/dt = 8π(2)(3) = 48π cm²/s.

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Question 18

Statistics

The table shows the distribution of ages of members of a cultural Troupe.
Age (years): 10 − 14, 15 − 19, 20 − 24, 25 − 29, 30 − 34
Frequency: 6, 8, 14, 10, 12
What is the class-mark of the median class?

  1. A.19
  2. B.22
  3. C.24
  4. D.32
Show the answer and explanation

Answer: B (22)

Explanation

There are 50 members; the 25th lies in 20 − 24 (cumulative 6, 14, 28). Its class mark is 22.

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Question 19

Statistics

The table shows the distribution of ages of members of a cultural Troupe.
Age (years): 10 − 14, 15 − 19, 20 − 24, 25 − 29, 30 − 34
Frequency: 6, 8, 14, 10, 12
In which group is the upper quartile?

  1. A.(15 − 19)
  2. B.(20 − 24)
  3. C.(25 − 29)
  4. D.(30 − 34)
Show the answer and explanation

Answer: C ((25 − 29))

Explanation

¾ × 50 = 37.5th member; cumulative frequencies 6, 14, 28, 38, so it is in 25 − 29.

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Question 20

Statistics

The table shows the distribution of ages of members of a cultural Troupe.
Age (years): 10 − 14, 15 − 19, 20 − 24, 25 − 29, 30 − 34
Frequency: 6, 8, 14, 10, 12
Find the mean of the distribution.

  1. A.23.4
  2. B.23.6
  3. C.24.3
  4. D.24.6
Show the answer and explanation

Answer: A (23.4)

Explanation

Class marks 12, 17, 22, 27, 32: Σfx = 72 + 136 + 308 + 270 + 384 = 1170. Mean = 1170/50 = 23.4.

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Question 21

Polynomials

If Px2 + (P + 1)x + P = 0 has equal roots, find the values of P.

  1. A.−1 and −1/3
  2. B.−1 and 1/3
  3. C.1 and −1/3
  4. D.1 and 1/3
Show the answer and explanation

Answer: C (1 and −1/3)

Explanation

Equal roots: (P + 1)² = 4P², so 3P² − 2P − 1 = 0, (3P + 1)(P − 1) = 0: P = 1 or −1/3.

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Question 22

Integration

Integrate (x − 1/x)2 with respect to x.

  1. A.(1/3)(x − 1/x)3 + C
  2. B.x3/3 − x − 1/x3 + C
  3. C.x3/3 − 2x + 1/x3 + C
  4. D.x3/3 − 2x − 1/x + C
Show the answer and explanation

Answer: D (x3/3 − 2x − 1/x + C)

Explanation

(x − 1/x)² = x² − 2 + x⁻². Integrating: x³/3 − 2x − 1/x + C.

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Question 23

Vectors

Given that AB = (4, 3) and AC = (2, −3) (column vectors), find |BC|.

  1. A.4√2
  2. B.6√2
  3. C.2√10
  4. D.4√10
Show the answer and explanation

Answer: C (2√10)

Explanation

BC = AC − AB = (−2, −6), |BC| = √40 = 2√10.

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Question 24

Vectors

Find the angle between (5i + 3j) and (3i − 5j).

  1. A.180°
  2. B.90°
  3. C.45°
  4. D.0°
Show the answer and explanation

Answer: B (90°)

Explanation

Dot product = 15 − 15 = 0, so the vectors are perpendicular: 90°.

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Question 25

Binomial Theorem

Find the coefficient of x3 in the binomial expansion of (3x + 4)4 in ascending powers of x.

  1. A.432
  2. B.194
  3. C.144
  4. D.108
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Answer: A (432)

Explanation

Term in x³: ⁴C₃ × 4 × (3x)³ = 4 × 4 × 27x³ = 432x³.

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Question 26

Probability

If a fair coin is tossed four times, what is the probability of obtaining at least one head?

  1. A.½
  2. B.¼
  3. C.13/16
  4. D.15/16
Show the answer and explanation

Answer: D (15/16)

Explanation

P(no head) = (½)⁴ = 1/16, so P(at least one) = 15/16.

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Question 28

Statistics

The deviations from the mean of a set of numbers are (k + 3)2, (k + 7), −2, k and (k + 2)2, where k is a constant. Find the value of k.

  1. A.3
  2. B.2
  3. C.−2
  4. D.−3
Show the answer and explanation

Answer: D (−3)

Explanation

Deviations from the mean add up to 0: 2k² + 12k + 18 = 0, i.e. (k + 3)² = 0, so k = −3.

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Question 29

Coordinate Geometry

Find the equation of a circle with centre (2, −3) and radius 2 units.

  1. A.x2 + y2 − 4x + 6y + 9 = 0
  2. B.x2 + y2 + 4x − 6y − 9 = 0
  3. C.x2 + y2 + 4x + 6y − 9 = 0
  4. D.x2 + y2 + 4x − 6y + 9 = 0
Show the answer and explanation

Answer: A (x2 + y2 − 4x + 6y + 9 = 0)

Explanation

(x − 2)² + (y + 3)² = 4 expands to x² + y² − 4x + 6y + 9 = 0.

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Question 30

Sequences and Series

The first term of a linear sequence is 9 and the common difference is 7. If the nth term is 380, find the value of n.

  1. A.45
  2. B.54
  3. C.56
  4. D.65
Show the answer and explanation

Answer: B (54)

Explanation

9 + 7(n − 1) = 380, so n − 1 = 53 and n = 54.

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Question 31

Polynomials

For what values of m is 9y2 + my + 4 a perfect square?

  1. A.±2√3
  2. B.±6√2
  3. C.+6
  4. D.+12
Show the answer and explanation

Answer: D (+12)

Explanation

A perfect square needs m² = 4 × 9 × 4 = 144, so m = ±12; of the options only +12 works ((3y + 2)²).

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Question 32

Dynamics

A particle accelerates at 12 ms−2 and travels a distance of 250m in 6 seconds. Find the initial velocity of the particles.

  1. A.5.7 ms−1
  2. B.6.0 ms−1
  3. C.6.0 ms−1
  4. D.77.5 ms−1
Show the answer and explanation

Answer: A (5.7 ms−1)

Explanation

s = ut + ½at²: 250 = 6u + 216, so u = 34/6 ≈ 5.7 m/s.

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Question 33

Permutations and Combinations

In how many ways can 9 people be seated on a bench if only 3 places are available?

  1. A.1200
  2. B.504
  3. C.320
  4. D.204
Show the answer and explanation

Answer: B (504)

Explanation

Order matters: ⁹P₃ = 9 × 8 × 7 = 504.

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Question 34

Statistics

Find the variance of 1, 2, 0, −3, 5, −2, 4.

  1. A.52/7
  2. B.40/7
  3. C.32/7
  4. D.27/7
Show the answer and explanation

Answer: A (52/7)

Explanation

Mean = 7/7 = 1. Squared deviations 0, 1, 1, 16, 16, 9, 9 add to 52, so variance = 52/7.

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Question 35

Coordinate Geometry

If the points (−1, t − 1), (t, t − 3) and (t − 6, 3) lie on the same straight line, find the values of t.

  1. A.t = −2 and −3
  2. B.t = 2 and 3
  3. C.t = −2 and 3
  4. D.t = 2 and −3
Show the answer and explanation

Answer: B (t = 2 and 3)

Explanation

Equal gradients: −2/(t + 1) = (4 − t)/(t − 5), which gives t² − 5t + 6 = 0, so t = 2 or 3.

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Question 36

Dynamics

A ball is thrown vertically upwards with a velocity of 15 ms−1. Calculate the maximum height reached. [Take g = 10 ms−2]

  1. A.15.25m
  2. B.13.25m
  3. C.11.25m
  4. D.10.25m
Show the answer and explanation

Answer: C (11.25m)

Explanation

At the top v = 0: 0 = 15² − 2(10)H, so H = 225/20 = 11.25 m.

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Question 37

Coordinate Geometry

Find the distance between the points (2, 5) and (5, 9).

  1. A.4 units
  2. B.5 units
  3. C.12 units
  4. D.14 units
Show the answer and explanation

Answer: B (5 units)

Explanation

√((5 − 2)² + (9 − 5)²) = √25 = 5 units.

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Question 38

Differentiation

Find limx→3 ((x3 + x2 − 12x)/(x2 − 9)).

  1. A.7/2
  2. B.0
  3. C.7/−2
  4. D.−7
Show the answer and explanation

Answer: A (7/2)

Explanation

x(x + 4)(x − 3)/((x − 3)(x + 3)) = x(x + 4)/(x + 3) → 3 × 7/6 = 7/2.

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Question 39

Trigonometry

Evaluate (tan 120° + tan 30°)/(tan 120° − tan 60°).

  1. A.√3 + √2
  2. B.2/3
  3. C.1/3
  4. D.−2√3
Show the answer and explanation

Answer: C (1/3)

Explanation

Numerator: −√3 + 1/√3 = −2/√3. Denominator: −√3 − √3 = −2√3. Ratio = 1/3.

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Question 40

Vectors

Express (14N, 240°) as a column vector. (Column vectors written as (x, y).)

  1. A.(−7, −7√3)
  2. B.(7√3, 7√3)
  3. C.(−7√3, −7)
  4. D.(7, −7√3)
Show the answer and explanation

Answer: C ((−7√3, −7))

Explanation

A bearing of 240°: x = 14 sin 240° = −7√3, y = 14 cos 240° = −7.

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Theory question 101

Indices and Logarithms

Solve (log2m)2 − log2m3 = 10.

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Model answer

Let p = log₂m: p² − 3p − 10 = 0, (p − 5)(p + 2) = 0.
p = 5: m = 2⁵ = 32.
p = −2: m = 2⁻² = ¼.

Explanation

log m³ = 3 log m turns it into a quadratic.

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Theory question 102

Binary Operations

A binary operation * is defined on the set of rational numbers by m * n = (m2 − n2)/(2mn), n ≠ 0 and m ≠ 0. (a) Find −3 * 2. (b) Show whether or not * is associative.

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Model answer

(a) −3 * 2 = (9 − 4)/(2(−3)(2)) = −5/12.
(b) Test with numbers: 1 * 2 = −3/4, so (1 * 2) * 3 = (9/16 − 9)/(2(−3/4)(3)) = 15/8.
2 * 3 = −5/12, so 1 * (2 * 3) = (1 − 25/144)/(2(1)(−5/12)) = −119/120.
15/8 ≠ −119/120, so * is not associative.

Explanation

One counter-example is enough to show an operation is not associative.

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Theory question 103

Polynomials

If α and β are the roots of 3x2 + 5x + 1 = 0, evaluate 27(α3 + β3).

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Model answer

α + β = −5/3, αβ = 1/3.
α³ + β³ = (α + β)³ − 3αβ(α + β) = −125/27 + 5/3 = −80/27.
27(α³ + β³) = −80.

Explanation

Express α³ + β³ using the sum and product of the roots.

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Theory question 104

Differentiation

Find the gradient of xy2 + x2y = 4xy at the point (1, 3).

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Model answer

y² + 2xy(dy/dx) + 2xy + x²(dy/dx) = 4y + 4x(dy/dx).
At (1, 3): 9 + 6y′ + 6 + y′ = 12 + 4y′, so 3y′ = −3.
Gradient = −1.

Explanation

Differentiate each product with the product rule.

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Theory question 105

Vectors

The position vectors of points P, Q and R are 11i + j, 5i + (13/3)j and 2i + 6j respectively. (a) Show that P, Q and R lie on a straight line. (b) Find the ratio |PQ| : |QR|.

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Model answer

(a) PQ = (−6, 10/3), QR = (−3, 5/3).
PQ = 2QR, so PQ and QR are parallel with Q in common: P, Q, R are collinear.
(b) |PQ| = 2√106/3, |QR| = √106/3, so |PQ| : |QR| = 2 : 1.

Explanation

Collinear points: one connecting vector is a multiple of the other.

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Theory question 106

Permutations and Combinations

A committee of 3 is formed from a panel of 5 men and 3 women. Find the: (a) number of ways of forming the committee; (b) probability that at least one woman is on the committee.

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Model answer

(a) ⁸C₃ = 56 ways.
(b) No woman: ⁵C₃ = 10, so P(at least one woman) = 1 − 10/56 = 46/56 = 23/28.

Explanation

'At least one' = 1 − P(none).

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Theory question 107

Statistics

The table shows the distribution of the lengths of 20 iron rods measured in metres.
Length (m): 1.0 − 1.1, 1.2 − 1.3, 1.4 − 1.5, 1.6 − 1.7, 1.8 − 1.9
Frequency: 2, 3, 8, 5, 2
Using an assumed mean of 1.45, calculate the mean of the distribution.

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Model answer

Class marks 1.05, 1.25, 1.45, 1.65, 1.85; d = −0.4, −0.2, 0, 0.2, 0.4.
Σfd = −0.8 − 0.6 + 0 + 1.0 + 0.8 = 0.4; Σf = 20.
Mean = 1.45 + 0.4/20 = 1.47 m.

Explanation

Mean = A + Σfd/Σf.

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Theory question 108

Statics

Find the direction of the resultant of the forces in the diagram.

Diagram for this question
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Model answer

Components (x, y): 10 N at 30° to the y-axis: (−5, 8.660); 8√2 N at 45°: (8, 8); 20 N at 60° below the negative x-axis: (−10, −17.321).
Resultant = (−7, −0.660).
It points 5.39° below the negative x-axis (tan⁻¹(0.660/7)): direction 185.4° from the positive x-axis, i.e. bearing 264.6°.

Explanation

Resolve every force into x and y components first.

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Theory question 109

Differentiation

(a) Differentiate (x − 3)(x2 + 5) with respect to x.
(b) If (x + 1)2 is a factor of f(x) = x3 + ax2 + bx + 3, where a and b are constants, find the: (i) values of a and b; (ii) zeros of f(x).

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Model answer

(a) d/dx = (x² + 5) + 2x(x − 3) = 3x² − 6x + 5.
(b)(i) f(x) = (x + 1)²(x + 3) (the constant term 3 fixes the third factor) = x³ + 5x² + 7x + 3, so a = 5, b = 7.
(ii) Zeros: −1 (twice) and −3.

Explanation

Compare coefficients after writing f(x) = (x + 1)²(x + c).

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Theory question 110

Surds

(a) Express (5 + √2)/(3 − √2) − (5 − √2)/(3 + √2) in the form a + b√2.
(b) Solve the following equations simultaneously using the determinant method: 3x − y − z = −2; x + 5y + 2z = 5; 2x + 3y + z = 0.

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Model answer

(a) (5 + √2)(3 + √2)/7 = (17 + 8√2)/7 and (5 − √2)(3 − √2)/7 = (17 − 8√2)/7.
Difference = 16√2/7: a = 0, b = 16/7.
(b) Δ = 1; Δₓ = −8; Δᵧ = 19; Δ_z = −41.
x = −8, y = 19, z = −41.

Explanation

Check the solution in all three equations.

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Theory question 111

Functions

(a) If f(x) = (x − 3)/(2x − 1), x ≠ ½ and g(x) = (x − 1)/(x + 1), x ≠ −1, find g o f.
(b)(i) Sketch the curve y = 9x − x3. (ii) Calculate the total area bounded by the x-axis and the curve y = 9x − x3.

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Model answer

(a) g(f(x)) = (f − 1)/(f + 1) = [(x − 3) − (2x − 1)]/[(x − 3) + (2x − 1)] = (−x − 2)/(3x − 4) = −(x + 2)/(3x − 4), x ≠ ½, 4/3.
(b)(i) Cuts the x-axis at −3, 0, 3; minimum at x = −√3, maximum at x = √3; falls to the right.
(ii) Area = 2∫₀³ (9x − x³) dx = 2(81/2 − 81/4) = 81/2 = 40.5 square units.

Explanation

Area below the axis is counted as positive.

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Theory question 113

Probability

The probabilities that Kofi, Kwasi and Ama will pass a certain examination are 9/10, 4/5 and x respectively. If the probability that only one of them will pass examination is 9/50, find the: (a) value of x; (b) probability that at least one of them will pass examination.

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Model answer

(a) Only one passes: (9/10)(1/5)(1 − x) + (1/10)(4/5)(1 − x) + (1/10)(1/5)x = 9/50.
9(1 − x) + 4(1 − x) + x = 9, so 13 − 12x = 9 and x = 1/3.
(b) P(all fail) = (1/10)(1/5)(2/3) = 1/75; P(at least one) = 74/75 ≈ 0.987.

Explanation

List the three 'only one passes' cases and add them.

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Theory question 114

Vectors

(a) Given that x = 3i − j, y = 2i + kj and the cosine of the angle between x and y is √5/5, find the values of the constant k.
(b) In the quadrilateral ABCD, AB = (5, −1), AC = (−6, −9) and BD = (4, −7) (column vectors). Show whether or not ABCD is a parallelogram.

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Model answer

(a) x·y = 6 − k; |x| = √10, |y| = √(4 + k²).
(6 − k)/(√10√(4 + k²)) = 1/√5 gives (6 − k)² = 2(4 + k²), k² + 12k − 28 = 0.
k = 2 or k = −14.
(b) Take A as origin: B = (5, −1), C = (−6, −9), D = B + BD = (9, −8).
DC = C − D = (−15, −1) ≠ AB = (5, −1) (also AD = (9, −8) ≠ BC = (−11, −8)).
Opposite sides are not equal vectors, so ABCD is not a parallelogram.

Explanation

A parallelogram ABCD needs AB = DC.

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Theory question 115

Statics

(a) A(−1, 2), B(3, 5) and C(4, 8) are the vertices of triangle ABC. Forces whose magnitudes are 5N and 3√10 N act along AB and CB respectively. Find the direction of the resultant of the forces.
(b) A particle starts from rest and moves in a straight line. It attains a velocity of 20 ms−1 after covering a distance of 8 metres. Calculate: (i) its acceleration; (ii) the time it will take to cover a distance of 40 metres.

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Model answer

(a) AB = (4, 3), |AB| = 5: force = (4, 3).
CB = (−1, −3), |CB| = √10: force = 3√10 × (−1, −3)/√10 = (−3, −9).
Resultant = (1, −6): 80.5° below the positive x-axis (279.5° anticlockwise from the x-axis; bearing 170.5°).
(b)(i) v² = 2as: 400 = 16a, a = 25 ms⁻².
(ii) 40 = ½(25)t², t² = 3.2, t ≈ 1.79 s.

Explanation

Force along a line = magnitude × unit vector of that line.

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