# How much interest did she earn? (compound interest)

#### Explanation:

Given:
Annual compound interest is 10%
Calculation cycle: 4 times a year.
Final sum in account: $600.00 after 4 years. Let the initial unknown principle sum be $P$Let the total interest in dollars be $x$Let the count of years be $n = 4$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ P(1+10/(nxx100))^(4n) =" total in the account"=$600

As the is a cycle of 4 calculations per year we have the indices of $4 n$

This is over 4 years so $n = 4$ giving:

P(1+10/(400))^(16) =$600 P(410/(400))^(16) =$600

P=$600-:(410/400)^(16) =$404.17496...

Rounding gives: P=$404.17 Thus the interest is the difference. $600.00
ul($404.17 larr" Subtract") $195.83

Jul 2, 2018