Harry runs 140 metres for 5 times. The average time taken for his first three runs is 17.9 seconds. He aims to have an average timing of 14.9 seconds for his five runs.
- What is the average time he needs to take for his 4th and 5th run in order to achieve his aim?
- If he runs 3 seconds faster in one of the five runs, what would be his average time for the five runs?
(a)
Total timing for first three runs
= 3 x 17.9
= 53.7 s
Total timing needed if the average is to be 14.9 s
= 14.9 x 5
= 74.5 s
Total timing for last two runs to achieve his aim
= 74.5 - 53.7
= 20.8 s
Average timing for last two runs
= 20.8 ÷ 2
= 10.4 s
(b)
New average
= (74.5 - 3) ÷ 5
= 14.3 s
Answer(s): (a) 10.4 s; (b) 14.3 s