Question

Jerry started doing sit-ups every day. The first day he did 13 sit-ups. Every day after that he did 2 more sit-ups than he had done the previous day. Today Jerry did 29 sit-ups. Write an equation that could be solved to find the number of days Jerry has been doing sit-ups, not counting the first day. Let n represent the number of days.

An equation that can help Jerry to find the number of days he has been doing sit-ups is given by

Answer 1

An equation that can help Jerry to find the number of days he has been doing sit-ups is
`(a_(n) -13)/(2) +1 = n`

Explanation:

First day = 13

Second day = first day + 2 = 13 +2 =15

Third day = second day + 2 = 17

Fourth day = Third day +2 = 19

So,

13 , 15 , 17, 19, 21, 23 ...........

The common difference is 2

By using arithmetic series

`a_(n) = 13 + (n-1)d`

where

`a_n` is the number of sit-ups done on the nth day

n is number of the days

d is the difference

Now

`a_(n) = 13 + (n-1)(2)`

`a_(n) -13 = (n-1)(2)`

`(a_(n) -13)/(2) = (n-1)`

`(a_(n) -13)/(2) +1 = n`