CTET 2 Math and Science Sep 2015 Paper

Question : 32 of 120

Marks: +1, -0

A sum of money amounts to ₹ 4,818 after 3 years and ₹ 7,227 after 6 years on compound interest. The sum is :

Solution:

A=P(1+\;\;{r}/{100})^{t}

(∵ A = Amount, P = Principal, r = Rate)
For 3 years

4818=P(1+\;\;{r}/{100})^{3}

......(i)
For 6 years

7227=P(1+\;\;{r}/{100})^{6}

......(ii)
Now, dividing eqn. (ii) by (i)

⇒\;\;{7227}/{4818}=\;\;{P(1+\;\;{r}/{100})^{6}}/{P(1+\;\;{r}/{100})^{3}}

⇒\;\;{7227}/{4818}=(1+\;\;{r}/{100})^{3}

\;\;{7227}/{4818}=\;\;{4818}/{P}

⇒7227×P=4818×4818

∴P=\;\;{4818×7818}/{7227}=3212

∴P=₹3212

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