Answer :
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.
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.