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At what rate per cent per annum will a sum of Rs. 15,625 amount to Rs. 21,952 in three years, if the interest is compounded annually?1. 12%2. 10%3. 9%4. 8% |
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Answer» Correct Answer - Option 1 : 12% Given: Principal (P) = Rs. 15625 Time (T) = 3 years Amount (A) = Rs. 21,952 Concept used: Amount = P(1 + R/100)T Calculation: Let the rate of interest per annum be R. 21952 = 15625(1 + R/100)3 ⇒ 21952/15625 = (1 + R/100)3 ⇒ ∛(21952/15625) = 1 + R/100 ⇒ 28/25 = 1 + R/100 ⇒ 28/25 – 1 = R/100 ⇒ (28 – 25)/25 = R/100 ⇒ 3/25 = R/100 ⇒ R = (3/25) × 100 ⇒ R = 3 × 4 ⇒ R = 12% ∴ The rate per cent per annum is 12%. |
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