The table shows the time taken by Ben to run 100 metres during his training sessions. After 4 attempts, Ben wanted to improve his average time taken by 0.3 seconds by running faster in the 5^th attempt. How fast should he run in the 5^th attempt in order for him to make the improvement?

Attempt	1st	2nd	3rd	4th	5th
Time taken  (in seconds)	21	15	20	20	?

Total time that Ben took for the first 4 attempts
= 21 + 15 + 20 + 20 
= 76 s

Average time that Ben took for the first 4 attempts
= 76 ÷ 4
= 19 s

New average time that Ben took for the 5 attempts
= 19 - 0.3
= 18.7 s

Total time that Ben took for the 5 attempts
= 5 x 18.7
= 93.5 s

Time that Ben should run in the 5^th attempt in order for him to make the improvement
= 93.5 - 76
= 17.5 s

Answer(s): 17.5 s