Carl runs 150 metres for 5 times. The average time taken for his first three runs is 17.4 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 5 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 17.4
= 52.2 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 - 52.2
= 22.3 s
Average timing for last two runs
= 22.3 ÷ 2
= 11.15 s
(b)
New average
= (74.5 - 5) ÷ 5
= 13.9 s
Answer(s): (a) 11.15 s; (b) 13.9 s