Answer: 10.67%
Step-by-step explanation:
Mr Madoff is offering to grow the current value of $1,000 to a future value of $1,500 in 4 years.
This is a future value problem.
1,500 = 1,000 * ( 1 + interest) ^ 4 years
( 1 + interest) ^ 4 = 1,500/1,000
( 1 + interest) = 4√(1,500/1,000)
1 + interest = 1.1066819197
Interest = 1.1066819197 - 1
= 10.67%