Answer: 33 years
Explanation:
Because 3% divided by a thousand is 0.03.
We can multiply that by the amount to get the total obtained by year.
0.03 x 12000 = 360
Now 12000 ÷ 360 = 33.3333...
So, 33 years.
We can also use the simple interest formula:
I = prt
I = interest
P = investment
R = interest rate
T = time
24000 = (12000) x (0.03) x T
T = 66.67
It would take 66 years for the interests gaining to reach 24000$, BUT we had 12000$ already, so if we divide 66.67 ÷ 2 = 33.33..
In 33 years we would have 12000$ + the main 12000$ so around 24000$ (should be more than 24k)