Fred runs 150 metres for 5 times. The average time taken for his first three runs is 17.1 seconds. He aims to have an average timing of 14.5 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 17.1
= 51.3 s
Total timing needed if the average is to be 14.5 s
= 14.5 x 5
= 72.5 s
Total timing for last two runs to achieve his aim
= 72.5 - 51.3
= 21.2 s
Average timing for last two runs
= 21.2 ÷ 2
= 10.6 s
(b)
New average
= (72.5 - 3) ÷ 5
= 13.9 s
Answer(s): (a) 10.6 s; (b) 13.9 s