A sum of Rs. 1200 at simple interest doubles itself in 8 years. The rate of interest is ______ percent per year.

This question was previously asked in
CISF Constable/Tradesmen (2019) Official Paper (Held On : 21 March 2021)
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  1. 8
  2. 10
  3. 12.5
  4. 11.5

Answer (Detailed Solution Below)

Option 3 : 12.5
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Detailed Solution

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Given:

P = 1200, T = 8 years

Formula Used:

Amount = Principal + Simple Interest

Simple interest = \(\frac{P× R× T}{100}\)

Calculation:

Using the above formula -

⇒ 2 × 1200 = 1200 + \(\frac{1200× R× 8}{100}\)

⇒ 2400 - 1200 = 96 R

⇒ 1200/96 = R = 12.5 %

∴ The correct answer is 12.5

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