Question

David invested $220 in a savings account that offers a 3% return on the investment. The value of David's investment will be at least $400 after a period of ________ years.
Hint: Use the formula A = P(1 + r)t, where A is the amount after t years, P is the amount invested, r is the rate of interest, and t is the time period.
Use a calculator to compute the answer, and round it off to the nearest year.

Answer 1

Principal amount invested by David = $220
Percentage of interest = 3%
Final amount = $400
Time of investment = t years
Then
A = P(1 + r)^t
400 = 220(1 + 0.03)^t
400 = 220(1.03)^t
(1.03)^t = 400/220
             = 20/11
t = 20.225 years
David's investment will be at least $400 after a period of 20.23 years.