gmatt1476
An investment has been growing at a fixed annual rate of 20% since it was first made; no portion of the investment has been withdrawn, and all interest has been reinvested. How much is the investment now worth?
(1) The value of the investment has increased by 44% since it was first made.
(2) If one year ago $600 had been withdrawn, today the investment would be worth 12% less than it is actually now worth.
DS24931.01
The investment is compounded. We need the amount now.
Annual rate of interest, r = 20%
(1) The value of the investment has increased by 44% since it was first made.
This means that the investment has completed 2 yrs (20% compounded over 2 yrs will give 44%). But we don't know the principal. We don't know how much was invested. So we don't know what it has become now. Not sufficient alone.
(2) If one year ago $600 had been withdrawn, today the investment would be worth 12% less than it is actually now worth.
If one year ago, 600 had been withdrawn, today the investment would be less by 600 and by the interest earned in the year on this 600 (which is 20% of 600 i.e. 120). So the total investment amount would have been less by $720 today. This 720 is 12% of the amount i.e.
12% of Total Amount = 720
Total Amount = $6000
Sufficient alone. (Note that we don't really need to do these calculations in the actual exam but we should know that we can calculate the total amount)
Answer (B)
Will2020! Regarding statement (1), I did some quick math to understand your explanation that 20% compounded in 2 years will give 44%. In fact, I used a smart number - $100 compounded by 20% annually - generating an amount of $144 (44% more than $100); but how can I realize that faster? How did you rationalise this? Thank you!