Question

2. Thom is training to run a 5K. In August he can complete a 5K in 50 minutes. InSeptember, after a month of training, he has managed to cut down his time by20%. At the race in October he manages to cut 20% off of his new time. After therace Thom gets lazy and does not run for six months. In April, he attemptsanother 5K and finds that his time has increased by 40% since October.Find Thom's 5K time in September.Find Thom's 5K time in October.Find Thom's 5K time in April.Find the overall percentage change in Thom's 5K time (from August untilApril).

Answer 1

September: 40 min

October: 32 min

April: 44.8 min

Percentage change: -10.4%

Step-by-step explanation:

In August, Thom complete a 5K in 50 minutes. In September, he cut down his time by 20%, so to calculate Thom's time in September, we need to calculate 20% of 50 minutes and subtract it from the initial time, so

50 min x 20% = 50 min x 20 / 100 = 1000/100 = 10 min

Then, the time in September is

50 min - 10 min = 40 min

In October, he cut 20% off of the 40 min that he has in September, so we can calculate Thom's time in October as

40 min x 20% = 40 min x 20 / 100 = 8 min

40 min - 8 min = 32 min

Finally, in April he increases his time by 40% since October, so the time in April is equal to

32 min x 40% = 32 x 40 / 100 = 12.8 min

32 min + 12.8 min = 44.8 min

Therefore, from August to April he goes from 50 minutes to 44.8 minutes. The overall percentage of change can be calculated as

`(44.8-50)/(50)*100=-10.4\text{ \%}`

So, he cut down his time by 10.4% from August to April.