A person invested a sum of ₹25,000 partly at 10% per annum simple interest and the rest at 12% per annum simple interest. At the end of 2 years, the total interest received was ₹5,640. The difference (in) between the two parts of the sum is:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 7,000.
Interest = P × R × T / 100
Total interest after 2 years = 5640
So:
(10×x×2)/100 + (12×(25000−x)×2)/100 = 5640
⇒ (20x)/100 + (600000 − 24x)/100 = 5640
⇒ (20x + 600000 − 24x)/100 = 5640
⇒ (−4x + 600000)/100 = 5640
⇒ −4x + 600000 = 564000
⇒ −4x = −36000 ⇒ x = 9000
So, invested at 10% = ₹9000
At 12% = ₹16000
Difference = ₹16000 − ₹9000 = ₹7000