Multiple choice

A certain sum of money amounts to Rs. 80 at 5% and to Rs. 40 at 2% per annum simple interest. Find the sum and the time.

  1. Rs. 26.67, 100 years

  2. Rs. 13.33, 50 years

  3. Rs. 13.33, 100 years

  4. Rs. 21.33, 100 years

  5. Rs. 21.33, 50 years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A = P + P*R*T/100. 80 = P + P*5*T/100 -> 80 = P(1 + 0.05T). 40 = P(1 + 0.02T). Divide: 2 = (1 + 0.05T)/(1 + 0.02T). 2 + 0.04T = 1 + 0.05T -> T = 100. P(1 + 0.02*100) = 40 -> 3P = 40 -> P = 13.33.

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