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Exercise 9 (B)
1. Calculate the amount and the compound interest by using the formula for compound interest.
Q.N. |
Principal |
Rate Of interest |
Time (In years) |
1 |
Rs 625 |
4 % p.a. |
2 |
2 |
Rs 1000 |
10 % p.a. |
3 |
3 |
Rs 8000 |
10 % half-yearly |
1.5 |
Q.1.Solution:
⇨ Given p=625 r=4 % n=2
⇨Then the annual Compound interest will be
⇨ Total Amount = P + C.I. = 625 + 51 =676 Rs
Q.2.Solution:
⇨ Given p=1000 r=10 % n=3
⇨ Then the annual Compound interest will be
⇨ Total Amount = P + C.I. = 1000 + 331 =1331 Rs
Q.3.Solution:
⇨ Given p=8000 r=10 % n=1.5 or 3/2
⇨ Then the Half-yearly Compound interest will be
⇨ Total Amount = P + C.I. = 8000 + 1261 =9261 Rs
Q.4. Reena and Ruchira borrowed Rs 60000 and Rs 50000 respectively for a period of 3 years. Reena paid simple interest at the rate of 10 % p.a., while Ruchira paid compound interest at the rate of 10 % p.a. Compounded annually.Who paid more interest and by how much ?
Solution:
⇨For Reena
⇨Given
⇨p = 60000
⇨r = 10 %
⇨n = 3 p.a.
⇨Given
⇨p = 60000
⇨r = 10 %
⇨n = 3 p.a.
⇨Therefore the Simple interest for Reena will be
Rs
⇨Given
⇨p = 50000
⇨r = 10 %
⇨n = 3 p.a.
⇨Therefore the Compound interest for Ruchira will be
Rs
⇨From above Reena paid more interest than Ruchira by
= Interest paid by Reena - Interest paid by Ruchira
= 18000 - 16550 = 1450 Rs
Q.5. Sangeeta lent Rs 40960 to Amar to purchase a shop at 12.5 % per annum. If the interest is compounded semi-annually, find the interest paid by Amar after 1.5 or 3/2 years ?
Solution:
⇨Given
⇨p=40960
⇨r=12.5 %
⇨n=1.5 or 3/2
⇨Then semi-annually Then the semi-annually Compound interest paid by Amar will be
Rs
Q.6. Sudhir lent Rs 2000 at compound interest at 10 % payable yearly, While Prashant lent Rs 2000 at compound interest at 10 % payable half yearly. Find the difference in the interest received by Sudhir and Prashant at the end of one year?
Solution:
⇨In case of Sudhir
⇨Given
⇨p=2000
⇨r=10 %
⇨n=1 p.a.
⇨Then the annual Compound interest paid by Sudhir will be
Rs
⇨In case of Prashant
⇨Given
⇨p=2000
⇨r=10 %
⇨n=1 Half-yearly.
⇨Given
⇨p=2000
⇨r=10 %
⇨n=1 Half-yearly.
⇨Then the half-yearly Compound interest paid by Prashant will be
Rs
⇨Therefore The difference in the interest received by Sudhir and Prashant at the end of one year Will be
= 205 - 200
= 5 Rs
Q.7. Find the difference between simple interest and compound interest on Rs 16000 for 1.5 rears or 3/2 years at 5 % per annum ,compound interest being reckoned half yearly.
Solution:
⇨Given
⇨p=16000
⇨r=5 %
⇨n=1.5 annul for S.I.
⇨The simple interest will be
Rs
⇨Given
⇨p=16000
⇨r=5 %
⇨n=1.5 Half-yearly for C.I
⇨The compound interest will be
⇨p=16000
⇨r=5 %
⇨n=1.5 Half-yearly for C.I
⇨The compound interest will be
Rs
⇨Therefore the difference between S.I and C.I will be
= C.I - S.I.
=1230.25 - 1200
=30.25 Rs
=1230.25 - 1200
=30.25 Rs
Q.8. Find the compound interest on 3125 for 3 years if the rates of interest for first, second and third year are respectively 4%, 5%, 6%.
Solution:
⇨Given
⇨p=3125
⇨r1=4 %
⇨r2=5%
⇨r3=6%
⇨n=3 years
⇨For different rates on successive years, Total amount 'A' will be
Q.9. A District contains 64000 inhabitants. If the population increases at the rate of 2.5 or 5/2 % per annum ,find the number of inhabitants at the end of 3 years.
Solution:
⇨Given
⇨p=64000
⇨r=2.5 %
⇨n=3
⇨The number of inhabitants at the end of 3 years
Rs
Q.10. The nagar palika of certain city started campaign to kill the stray dogs which numbered 1250 in the city as a result, the population of stray dogs started decreasing at the rate of 20 % per month . Calculate the number of stray dogs in the city three months after the campaign started.
Solution:
⇨p=1250
⇨r=20%
⇨n=3 months
⇨The number of stray dogs in the city three months after the campaign
started Will be
dogs
⇨Therefore no. of stray dogs=640
Q.11. The value of a machine depreciates each year by 10
% of it's value at the beginning of that year. It' value when
new is Rs 750, find it's value when it is 2 years old.
Solution:
⇨Given
⇨p=750
⇨r=10%
⇨n=2 months
⇨The value of a machine when it is 2 years old
will be
Rs
Q.12. The national wealth of a country increases by 4% of
it's value at the beginning of every year .Find the national
wealth of the country in 1985, if it was estimated as Rs 3.125
x 10^12 in 1983.
Solution:
⇨Given
⇨p=3.125 X 10^12
⇨r=4%
⇨n=2 years
⇨The national wealth of the country in 1984
Rs
⇨National wealth =3380 X 10^9 Rs
Q.13.The price of the scooter depreciates by 2% of it's at the
beginning of each year. Find The sale value of the scooter after 3
years , if it's present sale value is Rs 12000.
Solution:
⇨Given
⇨p=12000
⇨r=2%
⇨n=3 years
⇨The sale value of the scooter after 3 years will
be
Rs
⇨value of scooter=11294.304 Rs
Q.14. The population of Andhra Pradesh was 5.4 X 10^7 in
1988. If the population was growing at a constant rate of
2.4 % per annum .What was the population in 2008
A.D.[Given that (1.024)^20=1.60694].
Solution:
⇨Given
⇨p=5.4 X 10^7
⇨r=2.4%
⇨n=2008 - 1988 =20 years
⇨The population in 2008 will be
(approx)
Multiple Choice Questions
Q.15. A steno- typist deposits Rs 10000 in a bank
for a period of 3 years at 12 % per annum compound
interest . The interest accrued to her after
maturity will be
Solution:
⇨Given
⇨p=10000
⇨r=12%
⇨n=3 years
⇨The interest accrued to her after maturity will be
Rs
Q.16. The present population of a city is 180000. If
it increases at the rate of 8% per annum , It's population
after 2 years will be
Solution:
⇨Given
⇨p=180000
⇨r=8%
⇨n=2 years
⇨Population after 2 years will be
High Order Thinking
Q.17. Umesh set up a small factory by investing ₹40,000. During
the first three successive years his profits were 5%,10%
and 15% respectively. If each year the profit was on
previous years' capital, calculate his total profit.
Solution:
⇨Given
⇨p=40000
⇨r1=5%
⇨r2=10%
⇨r3=15%
⇨Simple interest for 1st year will be
Rs
⇨Total money invested in 2nd year=40000 + 2000 = 42000
Rs
⇨A/Q
⇨Profit in 2nd year =10%
⇨Then Simple interest for 2nd year will be
Rs
⇨Total money invested in 3rd year
= 42000 + 4200
= 46200 Rs
⇨Profit in 2nd year =15%
⇨Then Simple interest for 3rd year will be
Rs
⇨Total Money After 3 years
= 46200 + 6930
= 53130 Rs
⇨Therefore total profit will be
= 53130 - 40000
= 13130 Rs
⇨Given
⇨p=40000
⇨r1=5%
⇨r2=10%
⇨r3=15%
⇨Simple interest for 1st year will be
Rs
⇨Total money invested in 2nd year=40000 + 2000 = 42000
Rs
⇨A/Q
⇨Profit in 2nd year =10%
⇨Then Simple interest for 2nd year will be
Rs
⇨Total money invested in 3rd year
= 42000 + 4200
= 46200 Rs
⇨Profit in 2nd year =15%
⇨Then Simple interest for 3rd year will be
Rs
⇨Total Money After 3 years
= 46200 + 6930
= 53130 Rs
⇨Therefore total profit will be
= 53130 - 40000
= 13130 Rs
Q.18.The price value of the share of a company increase the
the rate of 15% in the first year suffered a loss of 10%
in the next year and again increased by 20% the third year
if the percent value of a share is Rs 2000 what will be
it's value after 3 years.
Solution:
⇨Given
⇨p=2000
⇨p=2000
⇨r1=15% increase
⇨r2=10% decrease
⇨r3=20% increase
⇨Simple interest after 1 year will be
Rs
⇨Share value after 1 year will be
= 2000 + 300
= 2300 Rs
⇨Simple interest after 2nd year will be
Rs
⇨Share value after 2nd year will be
= 2300 - 230
= 2070 Rs
⇨Simple interest after 3rd year will be
Rs
⇨Share value after 2nd year will be
= 2070 + 414
= 2484 Rs
Tags:
Math-Class-8