Riordan runs 100 metres for 5 times. The average time taken for his first three runs is 16.1 seconds. He aims to have an average timing of 14.3 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 4 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 16.1
= 48.3 s
Total timing needed if the average is to be 14.3 s
= 14.3 x 5
= 71.5 s
Total timing for last two runs to achieve his aim
= 71.5 - 48.3
= 23.2 s
Average timing for last two runs
= 23.2 ÷ 2
= 11.6 s
(b)
New average
= (71.5 - 4) ÷ 5
= 13.5 s
Answer(s): (a) 11.6 s; (b) 13.5 s