Question

The average time for four 400-meter runs was 53.4 seconds. If the first run was 52.7 seconds, the second run was 53.3 seconds, and the third run was 54.1 seconds, what was the time for the fourth run?

Answer 1

Answer: the time for the fourth run is 53.5 seconds.

Explanation:

Let t represent the time for the fourth run.

Average time = total time for the runs/the number of runs

From the information given,

Average time = 53.4 seconds

Number of runs = 4

Sum of the four runs = 52.7 + 53.3 + 54.1 + t = 160.1 + t

Therefore,

53.4 = (160.1 + t)/4

Cross multiplying by 4, it becomes

53.4 × 4 = 160.1 + t

213.6 = 160.1 + t

t = 213.6 - 160.1

t = 53.5 seconds

Answer 2

The time for the fourth run is 53.5 seconds

Explanation:

To calculate the average of the 4 runs, what we do is to add the time taken in the runs together and divide by 4.

Since we do not know the time for the 4th run, we can call it x.

Thus, mathematically;

(52.7+53.3+54.1+x)/4 = 53.4

(160.1+x) = 4(53.4)

160.1 + x = 213.6

x = 213.6 - 160.1

x = 53.5 seconds