Question

A is faster than B. A and B each walk 24 km. the sum of their speeds is 7 km/hr and the sum
of times taken by them is 14 hours. Then, A's speed is equal to
(a) 3 km/hr (b) 4 km/hr (c) 5 km/hr (d) 7 km/hr
​

Answer 1

Solutions :-　　

Let x and y km/h be their speeds respectively.

• Time taken by A = 24/x hours
• Time taken by B = 24/y hours

$\frac{24}{x} + \frac{24}{y} = 14 \\ 24(x + y) = 14xy$

But

$x + y = 7$

So

$24 \times 7 = 14xy$

$xy = 12$

Hence, we have to find two numbers such that their product is 12 and sum be 7. By Inspection the numbers are 4 and 3.

Their Speeds are 4 km/h and 3 km/h respectively.

• A's Speed = 4 km/h
• B's Speed = 3 km/h