Correct Answer - Option 2 : Rs. 6000
Given:
Amount after 3 years (A3) = Rs. 7200
Amount after 6 years (A6) = Rs. 8640
Formula used:
A = P × (1 + R/100)n
A is Amount, R is Rate percent per annum, n is time
Solution:
A6 = P × (1 + R/100)6 = 8640 ---- (1)
A3 = P × (1 + R/100)3 = 7200 ---- (2)
Dividing (1) by (2), we’ll get
\(⇒ \; \frac{{P \times {{\left( {1 + \frac{R}{{100}}} \right)}^6}}}{{P \times {{\left( {1 + \frac{R}{{100}}} \right)}^3}}} = \frac{{8640}}{{7200}}\)
⇒ (1 + R/100)3 = 6/5
Now putting the above value in (2) we’ll get
⇒ P × (6/5) = 7200
⇒ P = (7200 × 5)/6
⇒ P = 6000
∴ Sum invested is Rs. 6000