Tyr wrote:

christoph wrote:

In a km race, A gives B a start of 20 seconds and beats him by 40m. However, when he gives B a start of 25 seconds they finish in a dead heat. What is Aâ€™s speed in m/sec?

(1) 12.5 m/sec

(2) 20 m/sec

(3) 8 m/sec

(4) 10 m/sec

Poorly worded.

Are you sure A beats be by 40

minutes? A lot of confusion here with minutes/seconds.

Where is it stated that speed of A and B did not change?

The problem is correct . 40m is not 40 minutes. It is 40 meters

Here

A gives B a start of 20 seconds and beats him by 40m means B's speed is 40/20= 2m/s (it means when A travelled 1000mts B travelled only 960mts)

B's speed ---> 2m/s

Let speed of A be s1 and B be s2

From this "A gives B a start of 20 seconds and beats him by 40m "

we have s1(t - 20) = s2*t + 40(Since B is slow and still needs to run 40m)

--------(1)

s1*t = s2(t+25) (Since B gets a start of 25 sec) --(2)

Solve (1) and (2) and substitute s2 =2 and you get s1=8

A's speed = 8m/s