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In what time will the simple interest on ₹2200 at 6% per annum be the same as that on ₹1650 at 9% per annum in 10 years?

Solution

✅ Correct Option: 1

We have two investments:

  • Investment A: ₹2200 at 6% per annum (time unknown)
  • Investment B: ₹1650 at 9% per annum for 10 years

The simple interest on both investments must be equal.


For Investment B (₹1650 at 9% for 10 years):

Simple Interest =Principal×Rate×Time100= \dfrac{\text{Principal} \times \text{Rate} \times \text{Time}}{100}

SI=1650×9×10100\text{SI} = \dfrac{1650 \times 9 \times 10}{100}

SI=148500100\text{SI} = \dfrac{148500}{100}

SI=₹1485\text{SI} = ₹1485


For Investment A, the simple interest must also equal ₹1485.

Given:

  • Principal = ₹2200
  • Rate = 6%
  • Simple Interest = ₹1485
  • Time = ?

1485=2200×6×Time1001485 = \dfrac{2200 \times 6 \times \text{Time}}{100}

1485=13200×Time1001485 = \dfrac{13200 \times \text{Time}}{100}

1485=132×Time1485 = 132 \times \text{Time}

Time=1485132\text{Time} = \dfrac{1485}{132}

Time=11.25\text{Time} = 11.25 years


Converting to years and months:

11.2511.25 years =11= 11 years +0.25+ 0.25 years

0.25×12=30.25 \times 12 = 3 months

Therefore, the time required is 11 years and 3 months.

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