Jane's investment of $200 increased by 200% in 7 years when compounded annually. If she wants to earn an additional comp

[M7MBA]

Jane's investment of $200 increased by 200% in 7 years when compounded annually. If she wants to earn an additional compound interest of $4800, for how many more years should she keep her money invested?

A. 7 years
B. 14 years
C. 21 years
D. 24 years
E. 30 years

Answer: B

Source: e-GMAT

[Scott@TargetTestPrep]

Jane's investment of $200 increased by 200% in 7 years when compounded annually. If she wants to earn an additional compound interest of $4800, for how many more years should she keep her money invested?

A. 7 years
B. 14 years
C. 21 years
D. 24 years
E. 30 years

Answer: B

Solution:

We see that the original investment actually triples from $200 to $600 in 7 years . So it will triple again in another 7 years, from $600 to $1800. It will again triple in 7 more years, from $1800 to $5400. At this point, we see that the earning in additional interest is exactly 5400 - 600 = $4800. Therefore, it takes 7 + 7 = 14 additional years to earn $4800 after the investment accumulated to $600.

Answer: B