Question

Leaving home at the same time, Amal reaches office at 10: 15 am if he travels at 8 km/hr, and at 9: 40 am if he travels at 15 km/hr. Leaving home at 9: 10 am, at what speed, in km/hr, must he travel so as to reach office exactly at 10 am?

• A. 13
• B. 14
• C. 12
• D. 11

Answer 1

Answer: (C)

12

Answer 2

Let the speed in the first two cases be s and the distance be $d$.
Given,
$\frac{d}{8}-\frac{d}{15} = \frac{35}{60} ⇒ d = 10\; km$
Required speed = $\frac{10}{\frac{50}{60}}$ = $12$ kmph
So, the correct option is (C) : 12.