Question

Radha reaches company 10 min late when she travels at a speed of 20kmph and she reaches 20 min early if she travels at a speed of 30kmph. At what speed she should travel to cover the office distance in 2 hours?

1. 12 kmph
2. 15 kmph
3. 20 kmph
4. 25 kmph
5. 18 kmph

Answer 1

Correct Answer - Option 2 : 15 kmph

GIVEN :

Radha reaches company 10 min late when she travels at a speed of 20kmph

She reaches 20 min early if she travels at a speed of 30kmph.

 

CONCEPT :

Speed , Time & Distance

 

ASSUMPTION :

Let the office distance for Radha be M km.

 

CALCULATION :

Difference in time = 10 + 20 = 30 min = 30/60 hours

Relative speed = M/20 - M/30

⇒ M/20 - M/30 = 1/2

⇒ 10M/600 = 1/2

⇒ M = 30

The office distance for Radha is 30km.

∴ Required speed = distance/speed = 30/2 = 15kmph