Multiple choice

A sum of money amounts to Rs.12322.8 after 7 years and Rs.15724.8 after 12 years at the same rate of simple interest. What is the rate of interest per annum?

  1. 5%

  2. 7%

  3. 8%

  4. 10%

  5. 9%
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

After 7 years: P + SI(7) = 12322.8. After 12 years: P + SI(12) = 15724.8. Difference for 5 years = 15724.8 - 12322.8 = 3402. So SI for 5 years = 3402, meaning SI for 1 year = 3402/5 = 680.4. SI for 7 years = 680.4 x 7 = 4762.8. Principal = 12322.8 - 4762.8 = 7560. Rate = (680.4/7560) x 100 = 9%. Option E is correct.

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