CALCULUS!! HELP!?!?!?!?

Question

If you had $500 to invest at 8% interest per month, but had to withdraw $75 per month to pay your cell phone bill. How many months could you pay your bill in full?

please explain how you found the answer...THANKS A BUNCHES!!

Answer 1

Assume you withdraw the $75 after you receive the interest.

Then at the end of month 1 you have 500 + 500(1.067) -75

At the end of the 2nd month you would have [500+500(1.067)-75] *1.067- 75

Do you see the progression?

Set the formula for n months > 75

The value of n will be the the number you can pay your bill.

Answer 2

It would last you 9 months, after which you would have to go looking for extra cash

Your amount left at the end of each monthis is the amount that you start the month with multiplied by 1.08 and with 75 taken away.

So at the end of the first month, you have 500 x 1.08 - 75 = 465.

Second month 465 x 1.08 - 75 = 427.20

Quickest way is to knoch up an excel spreadsheet.

Formula would be =H2*1.08-75  where H2 is the cell where the money in your account at the start of each month is located

Probably not what you want as I haven't used calculus.  But hey, I did my best