Find the Sum.

The compound interest on a certain sum for 2 year is Rs 105 and simple interest is Rs 100. Find the sum.

  1. Rs. 300
  2.  Rs. 500
  3.  Rs. 400
  4.  Rs. 600
Desire Adnan Default Asked on 4th August 2015 in Maths.
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  • 1 Answer(s)

    Answer: (2) Rs.500
    Explanation:-
    Let the principal be Rs.X
    Given-
    Time = 2 years, Compound Interest = Rs.105   & Simple  Interest = Rs.100

    Formula-
    The ratio of Compound Interest & Simple Interest same sum at R %  for N  years .
    Then, C I /S I = R /N x 100 + 1

    Then,  105 / 100 = R / 2 x 100 + 1
    21 / 20 = R/ 200 + 1
    21 / 20 = (R + 200) / 200
    21 x 200 = (R + 200) x 20
    4200 = 20 R + 4000
    20 R = 4200 – 4000
    20 R = 200
    R = 200/20
    R = 10 %

    Formula-
    Simple Interest = P x R x T/100
    Where, P = principal , R = rate, & T = time.

    Then, 100 = X x 10 x 2 /100
    100 = 20 X /100
    20 X = 100 x 100
    20 X = 10000
    X = 10000/20
    X = 1000/2
    X = Rs.500

    Then, the sum is Rs.500
    Hence, the answer is (2) Rs.500.

    Anurag Mishra Professor Answered on 6th August 2015.
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