Question

You put $400 in an account account balance nine months later is now $418 what is the annual interest rate

Answer 1

6% a year

Explanation:

r=(1/t)(A/p-1)

r= 1/9((418/400)-1) = 0.005

0.005*100 (for percentage) = 0.5%

rate monthly is 0.5%

0.5*12= 6

yearly is 6%