A sum of money becomes ₹20070 after 3 year and ₹30105 after 6 years on compound interest. The sum will be
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 13380
We are given:
- Amount after 3 years: $A_3 = 20070$
- Amount after 6 years: $A_6 = 30105$
The compound interest formula:
$A = P(1 + r)^t$
Step 1: Express $A_6$ in terms of $A_3$
$A_6 = A_3 \cdot (1 + r)^3$
$30105 = 20070 \cdot (1 + r)^3$
$(1 + r)^3 = \frac{30105}{20070} \approx 1.5$
$1 + r = \sqrt[3]{1.5} \approx 1.1447$
Step 2: Find the principal P
$A_3 = P (1 + r)^3 ⇒20070 = P \cdot 1.1447^3$
But $1.1447^3 \approx 1.5$, so:
$20070 = P \cdot 1.5 ⇒P = \frac{20070}{1.5} \approx 13380$