Question

you invest $4000 in an account that pays simple interest of 4% for 10 years. how much will you have in 10 years?

Answer 1

I=PRT

find interst earned total and add to 4000

I=PRT
interest=principal times rate times time in years

principal=4000
rate=0.04
time in years=100
I=4000*0.04*10
I=1600 earned

add to total

4000+1600=$5600

Answer 2

Annual interest - 4%

interest in 1 year 
(4/100) * 4000
160

interest in 10 years
160 * 10
1600

So the amount you have at the end of 10 years
4000 + 1600
$ 5600