On his 12th birthday Enoch's grandparent's deposited $25 into a savings account for him. Each month after that up to and including his 20th birthday, they deposit $10 more than the previous month. How much money will Enoch have on his 20th birthday, excluding interest?

Question

I got $48,000, am I right?

Answer 1

96 months would be up to his 20th birthday, so it is 97 months as that is including his 20th birthday.

So the solution would be:
S97= 97/2 • [2(25) + (97-1)(10)]
S97=$48 985