# RS Aggarwal Class 8 Math Eleventh Chapter Compound Interest Exercise 11B Solution

## EXERCISE 11B

**By using the formula, find the amount and compound interest on:**

**(1) Rs 6000 for 2 years at 9% per annum compounded annually.**

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**(2) Rs 10000 for 2 years at 11% per annum compounded annually.**

**(3) Rs 31250 for 3 years at 8% per annum compounded annually.**

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**(4) Rs 10240 for 3 years at 12(1/2)% per annum compounded annually.**

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**(5) Rs 62500 for 2 years 6 months at 12% per annum compounded annually.**

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**(6) Rs 9000 for 2 years 4 months at 10% per annum compounded annually.**

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**(7) Find the amount of Rs 8000 for 2 years compounded annually and the rates being 9% per annum during the first year and 10% per annum during the second year.**

**(8) Anand obtained a loan of Rs 125000 from the Allahabad Bank for buying computers. The bank charges compound interest at 8% per annum, compounded annually. What amount will he have to pay after 3 years to clear the debt?**

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Ans: After 3 years he will pay Rs 157464 to clear the debt.

**(9) Three years ago, Beeru purchased a buffalo from Surjeet for Rs 11000. What payment will discharge his debt now, the rate of interest being 10% per annum, compounded annually?**

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Ans: Beeru payment Rs 14641 will discharge his debt now.

**(10) Shubhalaxmi took a loan of Rs 18000 from Surya Finance to purchase a TV set. If the company charges interest at 12% per annum during the first year and 12(1/2)% per annum during the second year, how much will she have to pay after 2 years?**

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Ans: Shubhalaxmi have to pay Rs 22680 after 2 years.

**(11) Neha borrowed Rs 24000 from the State Bank of India to buy a scooter. If the rate of interest be 10% per annum compounded annually, what payment will she have to make after 2 years 3 months?**

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Ans: Neha have to make Rs 29766 after 2 years 3 months.

**(12) Abhay borrowed Rs 16000 at 7(1/2)% per annum simple interest. On the same day, he lent it to Gurmeet at the same rate but compounded annually. What does he gain at the end of 2 years?**

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Ans: Abhay gain Rs 90 at the end of second year.

**(13) The simple interest on a sum of money for 2 years at 8% per annum is Rs 2400. What will be the compound interest on that sum at the same rate and for the same period?**

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Ans: The compound interest is Rs 2496.

**(14) The difference between the compound interest on a certain sum for 2 years at 6% per annum is Rs 90. Find the sum.**

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Ans: The required sum is Rs 25000.

**(15) The difference between the compound interest and the simple interest on a certain sum for 3 years at 10% annum is Rs 93. Find t he sum.**

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Ans: The required sum is Rs 3000.

**(16) A sum of money amounts to Rs 10240 in 2 years at 6(2/3)% per annum, compounded annually. Find the sum.**

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Ans: The required sum is Rs 9000.

**(17) What sum of money will amount to Rs 21296 in 3 years when compounded annually?**

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Ans: The required sum is Rs 16000.

**(18) At what rate per cent annum will Rs 4000 amount to Rs 4410 in 2 years when compounded annually?**

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Ans: The required rate is 5% p.a.

**(19) At what rate per cent per annum will Rs 640 amount to Rs 774.40 in 2 years when compounded annually?**

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Ans: The required rate is 10% p.a.

**(20) In how many years will Rs 1800 amount to Rs 2178 at 10% per annum when compounded annually?**

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Ans: The required time is 2 years.

**(21) In how many years will Rs 6250 amount to Rs 7290 at 8% per annum, compounded annually?**

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Ans: The required time is 2 years.

**(22) The population of a town is 125000. It is increasing at the rate of 2% per annum. What will be its population after 3 years?**

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Ans: The population after 3 years will be 132651.

**(23) Three years ago, the population of a town was 50000. If the annual increase during three successive years be at the rate of 5%, 4% and 3% respectively, what is its present population?**

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Ans: The present population is 56238.

**(24) The population of a city was 120000 in the year 2013. During next year it increased by 5% in the following year. What was its population in the year 2015?**

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Ans: In 2015 the population was 120840.

**(25) The count of bacteria in a certain experiment was increasing at the rate of 2% per hour. Find the bacteria at the end of 2hours if the count was initially 500000.**

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Ans: The number of bacteria is 520200.

**(26) The bacteria in a culture grows by 10% in the first hour. Find the bacteria at the end of 3 hours if the count was initially 20000.**

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Ans: The required bacteria 21780.

**(27) A machine is purchased for Rs 625000. Its value depreciates at the rate of 8% per annum. What will be its value after 2 years?**

Ans: The value after 2 year will be Rs 5290000.

**(28) A scooter is bought at Rs 56000. Its value depreciates at 10% per annum. What will be its value after 3 years?**

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Ans: The value after 3 year will be Rs 40824.

**(29) A car is purchased for Rs 348000. Its value depreciates at 10% per annum during the first year and at 20% per annum during the second year. What will be its value after 2 years?**

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Ans: The value after 2 year will be Rs 250560.

**(30) The value of machine depreciates at the rate of 10% per annum. It was purchased 3 years ago. If its present value is Rs 291600, for how much was it purchased? **

Ans: The value after 3 year will be Rs 400000.

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