Question

Alexander is taking part in a race. For the first 180 m he runs at 3 m/s. The remaining 240 m of the race takes him 100 seconds. What is Alexander's average speed, in m/s, over the whole race? If your answer is a decimal, give it to 2 d.p.​

Answer 1

Alexander's speed for the first 180 m is 3 m/s.

The remaining 240 m of the race takes him 100 seconds, which is an average speed of 240 m / 100 s = 2.4 m/s.

The average speed over the whole race is the total distance traveled divided by the total time taken.

The total distance traveled is 180 m + 240 m = 420 m.

The total time taken is 100 s + the time taken to run the first 180 m at 3 m/s, which is 100 s + (180 m / 3 m/s) = 100 s + 60 s = 160 s.

Therefore, Alexander's average speed over the whole race is 420 m / 160 s = 2.625 m/s.