how much money must be invested at 9% p.a to earn $720 in interest in 4 months?
assuming simple interest,
P * .09 * 4/12 = 720
if you are getting compound interest, then
P((1+.09/12)^4 - 1) = 720
In either case, solve for P
P * .09 * 4/12 = 720
if you are getting compound interest, then
P((1+.09/12)^4 - 1) = 720
In either case, solve for P