BTGmoderatorDC wrote: ↑Tue Jun 09, 2020 8:22 pm
A bank offers an interest of 5% per annum compounded annually on all its deposits. If $10,000 is deposited, what will be the ratio of the interest earned in the 4th year to the interest earned in the 5th year?
A. 1:5
B. 625:3125
C. 100:105
D. 100^4:105^4
E. 725:3225
OA
C
Solution:
The principal that earns interest in the 4th year is the total value of the investment at the end of the third year, which is 10,000 * (1 + 0.05)^3 = 10,000 * (1.05)^3. Thus, the interest earned at the 4th year is 5% of this amount, which is 10,000 * (1.05)^3 * (0.05).
Similarly, the principal that earns interest in the 5th year is the total value of the investment at the end of the fourth year, which is 10,000 * (1.05)^4. The interest earned at the 5th year is 5% of this amount, which is 10,000 * (1.05)^4 * 0.05.
Thus, the ratio of the interest earned in the 4th year to the interest earned in the 5th year is:
[10,000 * (1.05)^3 * (0.05)]/[10,000 * (1.05)^4 * 0.05]
1/1.05
100/105
Answer: C
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