Question

John looked at his bank account and noticed that he had $2,029.90 in his account. All that he could remember is that he created the account 7 years ago and that he had a 6% annual interest rate. How much money did John put into the account?

Answer 1

We will have that for the previous year, he had in the account:

`m_(y6)=2029.90-(2029.90\cdot6)/(100)\Rightarrow m_(y6)=1908.106`

For the year previous to that one, he had:

`m_(y5)=1908.106-(1908.106\cdot6)/(100)\Rightarrow m_(y5)=1793.61964`

For the previous year to that, he had:

`m_(y4)=1793.61964-(1793.61964\cdot6)/(100)\Rightarrow m_(y4)=1686.002462`

For the year previous to that one, he had:

`m_(y3)=1686.002462-(1686.002462\cdot6)/(100)\Rightarrow m_(y3)=1584.842314`

For the second year that the money was in the account, there was:

`m_(y2)=1584.842314-(1584.842314\cdot6)/(100)\Rightarrow m_(y2)=1489.751775`

And the orinial ammount of money that was in the account was:

`m_(y1)=1489.751775-(1489.751775\cdot6)/(100)\Rightarrow m_(y1)=1400.366669`

From this, we know that Jhon had originally $1400.37 in the bank account.