Sam put $2,000 in a savings account at his bank. After 10 years, his account balance was $4,000. The interest rate on the savings deposit is %. (Hint: Use the rule of 70 to solve this problem.)

Assuming this is based on simple interest, the answer would be 10% interest. The simple interest formula is P*r*T=i, when coupled with the principle value (2000), 4000 = 2000 + 2000 * r * 10

2000 = 20000 * r

2000/20000 = 1/10 = r