Question

A boy walks to his school at a distance of 6 km
with constant speed of 2.5 km h-1 and walks
-42 back with a constant speed of 4 kmh-1. His aver-
age speed for whole trip, expressed in
km h-?, is
(1) 1/2
(2) 3
(3) 24/13
(4) 40/13
​

Answer 1

Answer:

distance of school=6 km

speed while going to the school=2.5 km/h

∴t₁=6/2.5 hrs

now, distance travelled while coming back from school=6 km

speed=4 km/hr

now, t₂=6/4

we know that average speed = total distance travelled/total time taken

∴ total distance = 6+6=12

total time= 6/2.5+6/4=3.9 hr

now, average speed=                    12/3.9=40/13

∴correct answer is 40/13

Explanation: