Quantitative Aptitude
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Question 21
The difference between simple and compound interests compounded annually on a certain sum of money for 2 years at 4% per annum is Re. 1. The sum (in ₹) is:
Correct Answer: Option A
Let the sum be Rs. x. Then, C.I.
| = |  |
x |  |
1 + | 4 |  |
2 | - x |  |
= | |
676 | x | - x | |
= | 51 | x. |
| 100 | 625 | 625 |
| S.I. = | |
x x 4 x 2 | |
= | 2x | . |
| 100 | 25 |
| ∴ | 51x | - | 2x | = 1 |
| 625 | 25 |
⇒ x = 625.
Question 22
The compound interest on a sum for 2 years is ₹ 832 and the simple interest on the same sum for the same period is ₹ 800. The difference between the compound and simple interest for 3 years will be ?
Correct Answer: Option C
S.I. for first year = ₹ 400
S.I. on Rs .400 for 1 year = ₹ 32
∴ Rate = (interest x 100)/(principle x time) = (100 x 32)/(400 x 1) = 8%
Hence, the difference for 3rd year is S.I.on ₹ 832
= ₹(832 x 8/100)
= ₹ 66.56
∴ Total difference = ₹(32 + 66.56)
= ₹ 98.56
Question 23
The difference between the compound interest and the simple interest accrued on an amount of ₹ 18,000 in 2 year was ₹ 405. What was the rate of interest p.c.p.a ?
Correct Answer: Option A
Let the rate be R% p.a. Then,
|
18000 x | |
1 + | R | |
2 | - 18000 | |
- | |
18000 x R x 2 | |
||
| 100 | 100 |
⇒ 405
| ⇒ 18000 | |
|
1 + | R | |
2 | - 1 - | 2R | |
= 405 |
| 100 | 100 |
| ⇒ 15000 |  |
(100 + R)2 - 10000 - (200 x R) |  |
= 405 |
| 10000 |
| ⇒ R2 = | |
405 x 5 | |
= 225 |
| 9 |
⇒ R = 15.
∴ Rate = 15%.