Multiple choice

A sum of money kept in a bank amounts to Rs. $1000$ in $4$ years and Rs. $1400$ in $12$ years. Find the sum and interest carried every year.

  1. Rs. $ 600,$ Rs. $133\dfrac {1}{3}$
  2. Rs. $ 800,$ Rs. $50$
  3. Rs. $ 750,$ Rs. $150$
  4. Rs. $ 850,$ Rs. $75$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Simple interest: A = P + I. 1000 = P + 4I_year. 1400 = P + 12I_year. Subtracting: 400 = 8I_year, so I_year = 50. Then P = 1000 - 4*50 = 800.

AI explanation

Since the difference between the two amounts over the extra 8 years is simple interest, we calculate 1400 minus 1000 to get 400 as the interest for 8 years. Dividing 400 by 8 shows the interest carried every year is Rs. 50. Multiplying the 4-year interest of 200 and subtracting it from the 4-year amount of 1000 gives the original sum of Rs. 800.

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