Question

Shalu cycles to her school at an average speed of 12km/hr. It takes her 20 minutes to reach the school .if she wants to reach her school in 15 minutes, what should be her average speed?

Answer 1

case1:
speed = 12kmph.
time = 20 mins = 1/3 hours.
distance = speed × time = 12 × 1/3 = 4km.

case2:
distance = 4km.
time = 15 mins = 1/4 hours.
speed = distance ÷ time = 4 × 4 = 16 kmph.

Answer 2

Concept

Recall the relation between distance, speed and time is Distance=Speed×Time.

Given

Shalu rides her bike to school at a speed of 12 kilometers per hour. Her commute to school takes her 20 minutes.

To find

We have to find the average speed if she wants to get to school in 15 minutes.

Solution

She takes 20 minutes to reach the school at a 12 km/hr speed the distance of the school.

D = 12×20/60

   =4km

If she wants to cover same distance in 15 minutes then the average speed is,

S = 4/(15/60)

  = 4/(1/4)

  = 16 km

Hence if she covers the same distance in  15 minutes then the average speed is 16 km.