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RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.5                                                  PAGE NO: 14.31 
 
1. Ms. Cherian purchases a boat for Rs. 16000. If the total cost of the boat is 
depreciating at the rate of 5% per annum, calculate its value after 2 years. 
Solution: 
Given details are, 
Price of a boat is = Rs 16000 
Depreciation rate = 5% per annum 
By using the formula, 
A = P (1 + R/100) 
    = P (1 + R/100)
2
 
Since it is depreciation we use P (1 – R/100)
n
 
    = 16000 (1 – 5/100) (1 – 5/100) 
    = 16000 (95/100) (95/100) 
    = 16000 (0.95) (0.95) 
    = 14440 
? Value of the boat after two years is Rs 14440 
 
2. The value of a machine depreciates at the rate of 10% per annum. What will be 
its value 2 years hence, if the present value is Rs 100000? Also, find the total 
depreciation during this period. 
Solution: 
Given details are, 
Present value of machine is = Rs 100000 
Rate of depreciation = 10% per annum 
By using the formula, 
A = P (1 + R/100) 
    = 100000 (1 – 10/100) (1 – 10/100) 
    = 100000 (90/100) (90/100) 
    = 100000 (0.9) (0.9) 
    = 81000 
Value of machine after two years will be Rs 81000 
? Total depreciation during this period is Rs (100000 - 81000) = Rs 19000 
 
3. Pritam bought a plot of land for Rs. 640000. Its value is increasing by 5% of its 
previous value after every six months. What will be the value of the plot after 2 
years? 
Solution: 
Given details are, 
Page 2


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.5                                                  PAGE NO: 14.31 
 
1. Ms. Cherian purchases a boat for Rs. 16000. If the total cost of the boat is 
depreciating at the rate of 5% per annum, calculate its value after 2 years. 
Solution: 
Given details are, 
Price of a boat is = Rs 16000 
Depreciation rate = 5% per annum 
By using the formula, 
A = P (1 + R/100) 
    = P (1 + R/100)
2
 
Since it is depreciation we use P (1 – R/100)
n
 
    = 16000 (1 – 5/100) (1 – 5/100) 
    = 16000 (95/100) (95/100) 
    = 16000 (0.95) (0.95) 
    = 14440 
? Value of the boat after two years is Rs 14440 
 
2. The value of a machine depreciates at the rate of 10% per annum. What will be 
its value 2 years hence, if the present value is Rs 100000? Also, find the total 
depreciation during this period. 
Solution: 
Given details are, 
Present value of machine is = Rs 100000 
Rate of depreciation = 10% per annum 
By using the formula, 
A = P (1 + R/100) 
    = 100000 (1 – 10/100) (1 – 10/100) 
    = 100000 (90/100) (90/100) 
    = 100000 (0.9) (0.9) 
    = 81000 
Value of machine after two years will be Rs 81000 
? Total depreciation during this period is Rs (100000 - 81000) = Rs 19000 
 
3. Pritam bought a plot of land for Rs. 640000. Its value is increasing by 5% of its 
previous value after every six months. What will be the value of the plot after 2 
years? 
Solution: 
Given details are, 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
Price of land is = Rs 640000 
Rate of increase = 5% in every six month 
By using the formula, 
A = P (1 + R/100)
n
 
    = 640000 (1 + 5/100) (1 + 5/100) (1 + 5/100) (1 + 5/100) 
    = 640000 (105/100) (105/100) (105/100) (105/100) 
    = 640000 (1.025) (1.025) (1.025) (1.025) 
    = 706440.25 
? The value of the plot after two years will be Rs 706440.25 
 
4. Mohan purchased a house for Rs. 30000 and its value is depreciating at the rate of 
25% per year. Find the value of the house after 3 years. 
Solution: 
Given details are, 
Price of house is = Rs 30000 
Depreciation rate is = 25% per year 
By using the formula, 
A = P (1 + R/100)
n
 
    = 30000 (1 – 25/100) (1- 25/100) (1 – 25/100) 
    = 30000 (75/100) (75/100) (75/100)  
    = 30000 (0.75) (0.75) (0.75) 
    = 12656.25 
? The value of the house after 3 years is Rs 12656.25 
 
5. The value of a machine depreciates at the rate of 10% per annum. It was 
purchased 3 years ago. If its present value is Rs. 43740, find its purchase price. 
Solution: 
Given details are, 
Present value of machine is = Rs 43740 
Depreciation rate of machine is = 10% per annum 
Let the purchase price 3 years ago be = Rs x 
By using the formula, 
A = P (1 + R/100)
n
 
43740 = x (1 - 10/100) (1 - 10/100) (1 - 10/100) 
43740 = x (90/100) (90/100) (90/100) 
43740 = x (0.9) (0.9) (0.9) 
43740 = 0.729x 
x = 43740/0.729 
   = 60000 
Page 3


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.5                                                  PAGE NO: 14.31 
 
1. Ms. Cherian purchases a boat for Rs. 16000. If the total cost of the boat is 
depreciating at the rate of 5% per annum, calculate its value after 2 years. 
Solution: 
Given details are, 
Price of a boat is = Rs 16000 
Depreciation rate = 5% per annum 
By using the formula, 
A = P (1 + R/100) 
    = P (1 + R/100)
2
 
Since it is depreciation we use P (1 – R/100)
n
 
    = 16000 (1 – 5/100) (1 – 5/100) 
    = 16000 (95/100) (95/100) 
    = 16000 (0.95) (0.95) 
    = 14440 
? Value of the boat after two years is Rs 14440 
 
2. The value of a machine depreciates at the rate of 10% per annum. What will be 
its value 2 years hence, if the present value is Rs 100000? Also, find the total 
depreciation during this period. 
Solution: 
Given details are, 
Present value of machine is = Rs 100000 
Rate of depreciation = 10% per annum 
By using the formula, 
A = P (1 + R/100) 
    = 100000 (1 – 10/100) (1 – 10/100) 
    = 100000 (90/100) (90/100) 
    = 100000 (0.9) (0.9) 
    = 81000 
Value of machine after two years will be Rs 81000 
? Total depreciation during this period is Rs (100000 - 81000) = Rs 19000 
 
3. Pritam bought a plot of land for Rs. 640000. Its value is increasing by 5% of its 
previous value after every six months. What will be the value of the plot after 2 
years? 
Solution: 
Given details are, 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
Price of land is = Rs 640000 
Rate of increase = 5% in every six month 
By using the formula, 
A = P (1 + R/100)
n
 
    = 640000 (1 + 5/100) (1 + 5/100) (1 + 5/100) (1 + 5/100) 
    = 640000 (105/100) (105/100) (105/100) (105/100) 
    = 640000 (1.025) (1.025) (1.025) (1.025) 
    = 706440.25 
? The value of the plot after two years will be Rs 706440.25 
 
4. Mohan purchased a house for Rs. 30000 and its value is depreciating at the rate of 
25% per year. Find the value of the house after 3 years. 
Solution: 
Given details are, 
Price of house is = Rs 30000 
Depreciation rate is = 25% per year 
By using the formula, 
A = P (1 + R/100)
n
 
    = 30000 (1 – 25/100) (1- 25/100) (1 – 25/100) 
    = 30000 (75/100) (75/100) (75/100)  
    = 30000 (0.75) (0.75) (0.75) 
    = 12656.25 
? The value of the house after 3 years is Rs 12656.25 
 
5. The value of a machine depreciates at the rate of 10% per annum. It was 
purchased 3 years ago. If its present value is Rs. 43740, find its purchase price. 
Solution: 
Given details are, 
Present value of machine is = Rs 43740 
Depreciation rate of machine is = 10% per annum 
Let the purchase price 3 years ago be = Rs x 
By using the formula, 
A = P (1 + R/100)
n
 
43740 = x (1 - 10/100) (1 - 10/100) (1 - 10/100) 
43740 = x (90/100) (90/100) (90/100) 
43740 = x (0.9) (0.9) (0.9) 
43740 = 0.729x 
x = 43740/0.729 
   = 60000 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
? The purchase price is Rs 60000 
 
6. The value of a refrigerator which was purchased 2 years ago, depreciates at 12% 
per annum. If its present value is Rs. 9680, for how much was it purchased? 
Solution: 
Given details are, 
Present value of refrigerator is = Rs 9680 
Depreciation rate is = 12% 
Let the price of refrigerator 2 years ago be = Rs x 
By using the formula, 
A = P (1 + R/100)
n
 
9680 = x (1 – 12/100) (1 – 12/100) 
9680 = x (88/100) (88/100)  
9680 = x (0.88) (0.88) 
9680 = 0.7744x 
x = 9680/0.7744 
   = 12500 
? The refrigerator was purchased for Rs 12500 
 
7. The cost of a T.V. set was quoted Rs. 17000 at the beginning of 1999. In the 
beginning of 2000 the price was hiked by 5%. Because of decrease in demand the 
cost was reduced by 4% in the beginning of 2001. What was the cost of the T.V. set 
in 2001? 
Solution: 
Given details are, 
Cost of T.V at beginning of 1999 is = Rs 17000 
Hiked in price in the year 2000 is = 5% 
Depreciation rate in the year 2001 is = 4% 
By using the formula, 
A = P (1 + R/100)
n
 
    = 17000 (1 + 5/100) (1 – 4/100) 
    = 17000 (105/100) (96/100) 
    = 17000 (1.05) (0.96) 
    = 17136 
? The cost of TV set in the year 2001 is Rs 17136 
 
8. Ashish started the business with an initial investment of Rs. 500000. In the first 
year he incurred a loss of 4%. However during the second year he earned a profit of 
5% which in third year rose to 10%. Calculate the net profit for the entire period of 
Page 4


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.5                                                  PAGE NO: 14.31 
 
1. Ms. Cherian purchases a boat for Rs. 16000. If the total cost of the boat is 
depreciating at the rate of 5% per annum, calculate its value after 2 years. 
Solution: 
Given details are, 
Price of a boat is = Rs 16000 
Depreciation rate = 5% per annum 
By using the formula, 
A = P (1 + R/100) 
    = P (1 + R/100)
2
 
Since it is depreciation we use P (1 – R/100)
n
 
    = 16000 (1 – 5/100) (1 – 5/100) 
    = 16000 (95/100) (95/100) 
    = 16000 (0.95) (0.95) 
    = 14440 
? Value of the boat after two years is Rs 14440 
 
2. The value of a machine depreciates at the rate of 10% per annum. What will be 
its value 2 years hence, if the present value is Rs 100000? Also, find the total 
depreciation during this period. 
Solution: 
Given details are, 
Present value of machine is = Rs 100000 
Rate of depreciation = 10% per annum 
By using the formula, 
A = P (1 + R/100) 
    = 100000 (1 – 10/100) (1 – 10/100) 
    = 100000 (90/100) (90/100) 
    = 100000 (0.9) (0.9) 
    = 81000 
Value of machine after two years will be Rs 81000 
? Total depreciation during this period is Rs (100000 - 81000) = Rs 19000 
 
3. Pritam bought a plot of land for Rs. 640000. Its value is increasing by 5% of its 
previous value after every six months. What will be the value of the plot after 2 
years? 
Solution: 
Given details are, 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
Price of land is = Rs 640000 
Rate of increase = 5% in every six month 
By using the formula, 
A = P (1 + R/100)
n
 
    = 640000 (1 + 5/100) (1 + 5/100) (1 + 5/100) (1 + 5/100) 
    = 640000 (105/100) (105/100) (105/100) (105/100) 
    = 640000 (1.025) (1.025) (1.025) (1.025) 
    = 706440.25 
? The value of the plot after two years will be Rs 706440.25 
 
4. Mohan purchased a house for Rs. 30000 and its value is depreciating at the rate of 
25% per year. Find the value of the house after 3 years. 
Solution: 
Given details are, 
Price of house is = Rs 30000 
Depreciation rate is = 25% per year 
By using the formula, 
A = P (1 + R/100)
n
 
    = 30000 (1 – 25/100) (1- 25/100) (1 – 25/100) 
    = 30000 (75/100) (75/100) (75/100)  
    = 30000 (0.75) (0.75) (0.75) 
    = 12656.25 
? The value of the house after 3 years is Rs 12656.25 
 
5. The value of a machine depreciates at the rate of 10% per annum. It was 
purchased 3 years ago. If its present value is Rs. 43740, find its purchase price. 
Solution: 
Given details are, 
Present value of machine is = Rs 43740 
Depreciation rate of machine is = 10% per annum 
Let the purchase price 3 years ago be = Rs x 
By using the formula, 
A = P (1 + R/100)
n
 
43740 = x (1 - 10/100) (1 - 10/100) (1 - 10/100) 
43740 = x (90/100) (90/100) (90/100) 
43740 = x (0.9) (0.9) (0.9) 
43740 = 0.729x 
x = 43740/0.729 
   = 60000 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
? The purchase price is Rs 60000 
 
6. The value of a refrigerator which was purchased 2 years ago, depreciates at 12% 
per annum. If its present value is Rs. 9680, for how much was it purchased? 
Solution: 
Given details are, 
Present value of refrigerator is = Rs 9680 
Depreciation rate is = 12% 
Let the price of refrigerator 2 years ago be = Rs x 
By using the formula, 
A = P (1 + R/100)
n
 
9680 = x (1 – 12/100) (1 – 12/100) 
9680 = x (88/100) (88/100)  
9680 = x (0.88) (0.88) 
9680 = 0.7744x 
x = 9680/0.7744 
   = 12500 
? The refrigerator was purchased for Rs 12500 
 
7. The cost of a T.V. set was quoted Rs. 17000 at the beginning of 1999. In the 
beginning of 2000 the price was hiked by 5%. Because of decrease in demand the 
cost was reduced by 4% in the beginning of 2001. What was the cost of the T.V. set 
in 2001? 
Solution: 
Given details are, 
Cost of T.V at beginning of 1999 is = Rs 17000 
Hiked in price in the year 2000 is = 5% 
Depreciation rate in the year 2001 is = 4% 
By using the formula, 
A = P (1 + R/100)
n
 
    = 17000 (1 + 5/100) (1 – 4/100) 
    = 17000 (105/100) (96/100) 
    = 17000 (1.05) (0.96) 
    = 17136 
? The cost of TV set in the year 2001 is Rs 17136 
 
8. Ashish started the business with an initial investment of Rs. 500000. In the first 
year he incurred a loss of 4%. However during the second year he earned a profit of 
5% which in third year rose to 10%. Calculate the net profit for the entire period of 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
3 years. 
Solution: 
Given, 
Initial investment by Ashish is = Rs 500000 
Incurred loss in the first year is = 4% 
Profit in 2
nd
 year is = 5 % 
Profit in 3
rd
 year is = 10% 
By using the formula, 
A = P (1 + R/100)
n
 
    = 500000 (1 – 4/100) (1 + 5/100) (1 + 10/100) 
    = 500000 (96/100) (105/100) (110/100) 
    = 500000 (0.96) (1.05) (1.1) 
    = 554400 
? The net profit for the entire period of 3 years is Rs 554400 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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