Question

James wants to work up to doing 40 sit-ups a day. He plans to do 5 sit-ups the first day, 9 sit-ups the second day, 13 sit-ups the third day, and so on. On what day will he do 45 sit-ups?

Answer 1

45 = 5 + (n - 1) 4

solve for n will give you the day

Answer 2

day 1 5
2 9
3 13
4 17
and 45-17 = 28 more = 7 days

total 11 days

Answer 3

ok ?
this is an arithmetic series with common difference 4
nth term = a + (n-1)d where a = first term and d = common difference

thats where the equation 45 = comes from