Race

[jamesravid]

Three girls A, B and C run in a 100 m race. When A finishes, B is 10 m
behind A and when B finishes C is 20 m behind B.

All the athletes run at a constant speed. How far in metres was C from A when A finished?

[psuresh1982]

Here is the answer.....

Distance between C and A is 28 meter.

----------------------------
suresh.

[jamesravid]

That is the right answer. Give us your solution

[psuresh1982]

Let us assume A's average speed is 2m per second...

So A covered the distance in 20 sec...

B travelled the distance in 20 seconds is (100 - 10) = 90 meter.

B's average speed is 90/20 = 4.5 sec...

So B covered the distance in 22.222 seconds...

In that time C coverd only (100 -20) 80 meters....

C's average speed is 80/22.22222 = 3.6

Distance between A and C at that time A finished the race is ( 100 - (20 x 3.6)) = 28

[jamesravid]

I have a diff solution to this problem,

when B finishes C is 20 m behind B. This means C ran 80m when B covers 100m

When A finishes, B is 10 m behind A. This means B covered 90m when A finished 100m.
=> C covered 80% of 90m when A finished.
=> C ran for 72m.
=> C was 28m behind A when A finished the race.