Question

A boy is driving a car at a speed of 60 km/hr from his home to college. In the return journey, his speed was half of what it was in the ongoing journey. Calculate the total time of the entire journey. Given: Distance between college and home is 12 km. Also, find the average speed of the car for the entire journey. [5 MARKS]

Answer 1

Distance: 2 Marks
Average Speed: 1 Mark
Formula: 1 Mark
Steps: 1 Mark

From home to school:

Speed of car = 60 km/hr

Distance = 12 km

Time taken $=\frac{distance}{speed}=\frac{12}{60}=0.2hrs$

From school to home:

Speed of car $=\frac{60}{2}$= 30 km/hr

Distance = 12 km

Time taken $=\frac{12}{30}=\frac{2}{5}=0.4hrs$

Total time taken by car = 0.2 + 0.4 = 0.6 hrs
Average Speed $=\frac{TotalDistancetravelled}{TotalTime}$
$=\frac{24}{0.6}$
= 40 km/hr