Theory question 101
Ratio, Percentages and Rates(a) A car travels a distance of 112 km at an average speed of 70 km/h. It then travels further for 60 km at an average speed of 50 km/h. Calculate, for the entire journey, the total time taken.
(b) If x/y = 2 and y/z = 3, find the value of (x + y)/(y + z).
Show the model answer
Model answer
(a) Time for first part = 112 ÷ 70 = 1.6 h
Time for second part = 60 ÷ 50 = 1.2 h
Total time = 2.8 h = 2 hours 48 minutes
(b) x = 2y and z = y/3
(x + y)/(y + z) = 3y ÷ (4y/3) = 9/4 = 2¼
Explanation
Time = distance ÷ speed for each part; then write x and z in terms of y.