-
A certain sum doubles in 7 years at simple interest. The same sum under the same interest rate will become 4 times in how many years.
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- 14
- 28
- 21
- 10
- 14
Correct Option: C
According to question ,
Case I,
Here , T = 7 years
Simple Interest = Principal
| Rate = | |
| Principal × Time |
| Rate = | % per annum | |
| 7 |
Case II,
Here , R = ( 100 / 7 )%
Simple Interest = 3 × Principal
| Time = | |
| Principal × Rate |
| Time = | |
| 7 | |
Time = 3 × 7 = 21 years
