Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by a bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is

AcademicPhysicsNCERTClass 7

As given,

Distance between home and school $=3\ km$

Time to reach school $=30\ minutes=\frac{1}{2}\ h$

Time taken to come back from the school $=20\ m=\frac{20}{60}\ h=\frac{1}{3}\ h$

So, the average speed of the Boojho $=\frac{total\ distance}{total time}$

$=\frac{3\ km+3\ km}{\frac{1}{2}\ h+\frac{1}{3}\ h}$

$=\frac{6\ km}{\frac{5}{6}\ h}$

$=\frac{36}{5}\ km/h$

$=7.2\ km/h$

Updated on 10-Oct-2022 12:47:27