a student is moving from home to school at 20 km per hour and on his return from school to home at 30 km per hour calculate the average speed
Answers
A student is moving with a speed of 20 km/hr from home to school and with a speed of 30 km from school to home.
We have to find the average speed of the boy.
Let us assume that the distance covered by a student is 'x' km.
Average speed is defined as the ratio of total distance covered with respect to total time taken.
Total distance covered by student = Distance covered by student from (home to school + school to home)
= x + x = 2x
Also,
Time = Distance/Speed
From home to school:
t1 = x/20 hr
From school to home:
t2 = x/30 hr
Total time = t1 + t2
= x/20 + x/30
= (3x + 2x)/60
= 5x/60
Therefore, Average speed of the boy = (Total distance covered)/(Total time taken)
= 2x/(5x/60)
= (2x × 60)/5x
= 2*12 = 24 km/hr
Shortcut Method:
S1 = 20 km/hr and S2 = 30 km/hr
Average speed = (2 × S1 × S2)/(S1 + S2)
= (2 × 20 × 30)/(20 + 30)
= 1200/50
= 24 km/hr
hii maine aise hi solve kiya h
