Answer:
33.3%
Explanation:
Simple Interest = Principal * Rate * Time/100
Amount = Principal + Interest
If $120 doubles in approximately 13 years, then the amount after 13years = 2*$120 = $240
Interest = $240-$120
Interest = $120
120 = 120*Rate * 13/100
1 = 13Rate/100
13rate = 100
rate = 100/3
rate = 33.3%
Hence the interest rate is 33.3%