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JAMB Mathematics 1988 Question 34

Question 34

Mensuration of Plane Shapes

A quadrant of a circle of radius 6cm is cut away from each corner of rectangle 25cm long and 18cm wide. Find the perimeter of the remaining figure.

  1. A.38cm
  2. B.(38 + 12π)cm
  3. C.(86 − 12π)cm
  4. D.(86 − 6π)cm
Show the answer and explanation

Answer: B ((38 + 12π)cm)

Explanation

The rectangle's perimeter is 86cm. Each corner loses 6 + 6 = 12cm of straight edge (48cm in all) and gains a quarter arc of 2π × 6 ÷ 4 = 3π. Perimeter = 86 − 48 + 12π = (38 + 12π)cm.