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The simple interest on a certain sum of money for 21/2 yr at 12% per annum is ₹ 20 less than the simple interest on the same sum for 31/2 yr at 10% per annum. Find the sum.
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- ₹ 800
- ₹ 750
- ₹ 625
- ₹ 400
- None of the above
Correct Option: D
Given, T1 = 5/2, R1= 12% T2= 7/2 yr and R2 = 10%
Let the sum be P.
Then, [(P x 10 x 7)/(100 x 2)] - [(P x 12 x 5)/(100 x 2)] = 20
⇒ (7P/20) - (3P/10) = 20
∴ P = 20 x 20 = ₹ 400
