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 Page 1


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.2                                                  PAGE NO: 14.14 
 
1. Compute the amount and the compound interest in each of the following by using 
the formulae when : 
(i) Principal = Rs 3000, Rate = 5%, Time = 2 years 
(ii) Principal = Rs 3000, Rate = 18%, Time = 2 years 
(iii) Principal = Rs 5000, Rate = 10 paise per rupee per annum, Time = 2 years 
(iv) Principal = Rs 2000, Rate = 4 paise per rupee per annum, Time = 3 years 
(v) Principal = Rs 12800, Rate = 7 ½ %, Time = 3 years 
(vi) Principal = Rs 10000, Rate = 20% per annum compounded half-yearly, Time = 
2 years 
(vii) Principal = Rs 160000, Rate = 10 paise per rupee per annum compounded half 
yearly, Time = 2 years. 
Solution: 
By using the formula, 
A = P (1 + R/100)
 n
 
Let us solve 
(i) Given, P = Rs 3000, rate = 5%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 5/100)
2
 
    = 3000 (105/100)
2
 
    = Rs 3307.5 
Compound interest (CI) = A-P = Rs 3307.5 – 3000 = Rs 307.5 
 
(ii) Given, P = Rs 3000, rate = 18%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 18/100)
2
 
    = 3000 (118/100)
2
 
    = Rs 4177.2 
Compound interest (CI) = A-P = Rs 4177.2 – 3000 = Rs 1177.2 
 
(iii) Given, P = Rs 5000, rate = 10%, time = 2years 
A = P (1 + R/100)
 n
 
    = 5000 (1 + 10/100)
2
 
    = 5000 (110/100)
2
 
    = Rs 6050 
Compound interest (CI) = A-P = Rs 6050 – 5000 = Rs 1050 
 
(iv) Given, P = Rs 2000, rate = 4%, time = 3years 
Page 2


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.2                                                  PAGE NO: 14.14 
 
1. Compute the amount and the compound interest in each of the following by using 
the formulae when : 
(i) Principal = Rs 3000, Rate = 5%, Time = 2 years 
(ii) Principal = Rs 3000, Rate = 18%, Time = 2 years 
(iii) Principal = Rs 5000, Rate = 10 paise per rupee per annum, Time = 2 years 
(iv) Principal = Rs 2000, Rate = 4 paise per rupee per annum, Time = 3 years 
(v) Principal = Rs 12800, Rate = 7 ½ %, Time = 3 years 
(vi) Principal = Rs 10000, Rate = 20% per annum compounded half-yearly, Time = 
2 years 
(vii) Principal = Rs 160000, Rate = 10 paise per rupee per annum compounded half 
yearly, Time = 2 years. 
Solution: 
By using the formula, 
A = P (1 + R/100)
 n
 
Let us solve 
(i) Given, P = Rs 3000, rate = 5%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 5/100)
2
 
    = 3000 (105/100)
2
 
    = Rs 3307.5 
Compound interest (CI) = A-P = Rs 3307.5 – 3000 = Rs 307.5 
 
(ii) Given, P = Rs 3000, rate = 18%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 18/100)
2
 
    = 3000 (118/100)
2
 
    = Rs 4177.2 
Compound interest (CI) = A-P = Rs 4177.2 – 3000 = Rs 1177.2 
 
(iii) Given, P = Rs 5000, rate = 10%, time = 2years 
A = P (1 + R/100)
 n
 
    = 5000 (1 + 10/100)
2
 
    = 5000 (110/100)
2
 
    = Rs 6050 
Compound interest (CI) = A-P = Rs 6050 – 5000 = Rs 1050 
 
(iv) Given, P = Rs 2000, rate = 4%, time = 3years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
A = P (1 + R/100)
 n
 
    = 2000 (1 + 4/100)
3
 
    = 2000 (104/100)
3
 
    = Rs 2249.72 
Compound interest (CI) = A-P = Rs 2249.72 – 2000 = Rs 249.72 
 
(v) Given, P = Rs 12800, rate = 7 ½ % = 15/2% = 7.5%, time = 3years 
A = P (1 + R/100)
 n
 
    = 12800 (1 + 7.5/100)
3
 
    = 12800 (107.5/100)
3
 
    = Rs 15901.4 
Compound interest (CI) = A-P = Rs 15901.4 – 12800 = Rs 3101.4 
 
(vi) Given, P = Rs 10000, rate = 20 % = 20/2 = 10% (quarterly), time = 2years = 2 × 2 = 
4years 
A = P (1 + R/100)
 n
 
    = 10000 (1 + 10/100)
4
 
    = 10000 (110/100)
4
 
    = Rs 14641 
Compound interest (CI) = A-P = Rs 14641 – 10000 = Rs 4641 
 
(vii) Given, P = Rs 160000, rate = 10% = 10/2% = 5% (half yearly), time = 2years = 2×2 
= 4 quarters 
A = P (1 + R/100)
 n
 
    = 160000 (1 + 5/100)
4
 
    = 160000 (105/100)
4
 
    = Rs 194481 
Compound interest (CI) = A-P = Rs 194481 – 160000 = Rs 34481 
 
2. Find the amount of Rs. 2400 after 3 years, when the interest is compounded 
annually at the rate of 20% per annum. 
Solution: 
Given details are, 
Principal (p) = Rs 2400 
Rate (r) = 20% per annum 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 2400 (1 + 20/100)
3
 
Page 3


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.2                                                  PAGE NO: 14.14 
 
1. Compute the amount and the compound interest in each of the following by using 
the formulae when : 
(i) Principal = Rs 3000, Rate = 5%, Time = 2 years 
(ii) Principal = Rs 3000, Rate = 18%, Time = 2 years 
(iii) Principal = Rs 5000, Rate = 10 paise per rupee per annum, Time = 2 years 
(iv) Principal = Rs 2000, Rate = 4 paise per rupee per annum, Time = 3 years 
(v) Principal = Rs 12800, Rate = 7 ½ %, Time = 3 years 
(vi) Principal = Rs 10000, Rate = 20% per annum compounded half-yearly, Time = 
2 years 
(vii) Principal = Rs 160000, Rate = 10 paise per rupee per annum compounded half 
yearly, Time = 2 years. 
Solution: 
By using the formula, 
A = P (1 + R/100)
 n
 
Let us solve 
(i) Given, P = Rs 3000, rate = 5%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 5/100)
2
 
    = 3000 (105/100)
2
 
    = Rs 3307.5 
Compound interest (CI) = A-P = Rs 3307.5 – 3000 = Rs 307.5 
 
(ii) Given, P = Rs 3000, rate = 18%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 18/100)
2
 
    = 3000 (118/100)
2
 
    = Rs 4177.2 
Compound interest (CI) = A-P = Rs 4177.2 – 3000 = Rs 1177.2 
 
(iii) Given, P = Rs 5000, rate = 10%, time = 2years 
A = P (1 + R/100)
 n
 
    = 5000 (1 + 10/100)
2
 
    = 5000 (110/100)
2
 
    = Rs 6050 
Compound interest (CI) = A-P = Rs 6050 – 5000 = Rs 1050 
 
(iv) Given, P = Rs 2000, rate = 4%, time = 3years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
A = P (1 + R/100)
 n
 
    = 2000 (1 + 4/100)
3
 
    = 2000 (104/100)
3
 
    = Rs 2249.72 
Compound interest (CI) = A-P = Rs 2249.72 – 2000 = Rs 249.72 
 
(v) Given, P = Rs 12800, rate = 7 ½ % = 15/2% = 7.5%, time = 3years 
A = P (1 + R/100)
 n
 
    = 12800 (1 + 7.5/100)
3
 
    = 12800 (107.5/100)
3
 
    = Rs 15901.4 
Compound interest (CI) = A-P = Rs 15901.4 – 12800 = Rs 3101.4 
 
(vi) Given, P = Rs 10000, rate = 20 % = 20/2 = 10% (quarterly), time = 2years = 2 × 2 = 
4years 
A = P (1 + R/100)
 n
 
    = 10000 (1 + 10/100)
4
 
    = 10000 (110/100)
4
 
    = Rs 14641 
Compound interest (CI) = A-P = Rs 14641 – 10000 = Rs 4641 
 
(vii) Given, P = Rs 160000, rate = 10% = 10/2% = 5% (half yearly), time = 2years = 2×2 
= 4 quarters 
A = P (1 + R/100)
 n
 
    = 160000 (1 + 5/100)
4
 
    = 160000 (105/100)
4
 
    = Rs 194481 
Compound interest (CI) = A-P = Rs 194481 – 160000 = Rs 34481 
 
2. Find the amount of Rs. 2400 after 3 years, when the interest is compounded 
annually at the rate of 20% per annum. 
Solution: 
Given details are, 
Principal (p) = Rs 2400 
Rate (r) = 20% per annum 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 2400 (1 + 20/100)
3
 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
    = 2400 (120/100)
3
 
    = Rs 4147.2 
? Amount is Rs 4147.2 
 
3. Rahman lent Rs. 16000 to Rasheed at the rate of 12 ½ % per annum compound 
interest. Find the amount payable by Rasheed to Rahman after 3 years. 
Solution: 
Given details are, 
Principal (p) = Rs 16000 
Rate (r) = 12 ½ % per annum = 12.5% 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 16000 (1 + 12.5/100)
3
 
    = 16000 (112.5/100)
3
 
    = Rs 22781.25 
? Amount is Rs 22781.25 
 
4. Meera borrowed a sum of Rs. 1000 from Sita for two years. If the rate of interest 
is 10% compounded annually, find the amount that Meera has to pay back. 
Solution: 
Given details are, 
Principal (p) = Rs 1000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 1000 (1 + 10/100)
2
 
    = 1000 (110/100)
2
 
    = Rs 1210 
? Amount is Rs 1210 
 
5. Find the difference between the compound interest and simple interest. On a sum 
of Rs. 50,000 at 10% per annum for 2 years. 
Solution: 
Given details are, 
Principal (p) = Rs 50000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
Page 4


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.2                                                  PAGE NO: 14.14 
 
1. Compute the amount and the compound interest in each of the following by using 
the formulae when : 
(i) Principal = Rs 3000, Rate = 5%, Time = 2 years 
(ii) Principal = Rs 3000, Rate = 18%, Time = 2 years 
(iii) Principal = Rs 5000, Rate = 10 paise per rupee per annum, Time = 2 years 
(iv) Principal = Rs 2000, Rate = 4 paise per rupee per annum, Time = 3 years 
(v) Principal = Rs 12800, Rate = 7 ½ %, Time = 3 years 
(vi) Principal = Rs 10000, Rate = 20% per annum compounded half-yearly, Time = 
2 years 
(vii) Principal = Rs 160000, Rate = 10 paise per rupee per annum compounded half 
yearly, Time = 2 years. 
Solution: 
By using the formula, 
A = P (1 + R/100)
 n
 
Let us solve 
(i) Given, P = Rs 3000, rate = 5%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 5/100)
2
 
    = 3000 (105/100)
2
 
    = Rs 3307.5 
Compound interest (CI) = A-P = Rs 3307.5 – 3000 = Rs 307.5 
 
(ii) Given, P = Rs 3000, rate = 18%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 18/100)
2
 
    = 3000 (118/100)
2
 
    = Rs 4177.2 
Compound interest (CI) = A-P = Rs 4177.2 – 3000 = Rs 1177.2 
 
(iii) Given, P = Rs 5000, rate = 10%, time = 2years 
A = P (1 + R/100)
 n
 
    = 5000 (1 + 10/100)
2
 
    = 5000 (110/100)
2
 
    = Rs 6050 
Compound interest (CI) = A-P = Rs 6050 – 5000 = Rs 1050 
 
(iv) Given, P = Rs 2000, rate = 4%, time = 3years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
A = P (1 + R/100)
 n
 
    = 2000 (1 + 4/100)
3
 
    = 2000 (104/100)
3
 
    = Rs 2249.72 
Compound interest (CI) = A-P = Rs 2249.72 – 2000 = Rs 249.72 
 
(v) Given, P = Rs 12800, rate = 7 ½ % = 15/2% = 7.5%, time = 3years 
A = P (1 + R/100)
 n
 
    = 12800 (1 + 7.5/100)
3
 
    = 12800 (107.5/100)
3
 
    = Rs 15901.4 
Compound interest (CI) = A-P = Rs 15901.4 – 12800 = Rs 3101.4 
 
(vi) Given, P = Rs 10000, rate = 20 % = 20/2 = 10% (quarterly), time = 2years = 2 × 2 = 
4years 
A = P (1 + R/100)
 n
 
    = 10000 (1 + 10/100)
4
 
    = 10000 (110/100)
4
 
    = Rs 14641 
Compound interest (CI) = A-P = Rs 14641 – 10000 = Rs 4641 
 
(vii) Given, P = Rs 160000, rate = 10% = 10/2% = 5% (half yearly), time = 2years = 2×2 
= 4 quarters 
A = P (1 + R/100)
 n
 
    = 160000 (1 + 5/100)
4
 
    = 160000 (105/100)
4
 
    = Rs 194481 
Compound interest (CI) = A-P = Rs 194481 – 160000 = Rs 34481 
 
2. Find the amount of Rs. 2400 after 3 years, when the interest is compounded 
annually at the rate of 20% per annum. 
Solution: 
Given details are, 
Principal (p) = Rs 2400 
Rate (r) = 20% per annum 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 2400 (1 + 20/100)
3
 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
    = 2400 (120/100)
3
 
    = Rs 4147.2 
? Amount is Rs 4147.2 
 
3. Rahman lent Rs. 16000 to Rasheed at the rate of 12 ½ % per annum compound 
interest. Find the amount payable by Rasheed to Rahman after 3 years. 
Solution: 
Given details are, 
Principal (p) = Rs 16000 
Rate (r) = 12 ½ % per annum = 12.5% 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 16000 (1 + 12.5/100)
3
 
    = 16000 (112.5/100)
3
 
    = Rs 22781.25 
? Amount is Rs 22781.25 
 
4. Meera borrowed a sum of Rs. 1000 from Sita for two years. If the rate of interest 
is 10% compounded annually, find the amount that Meera has to pay back. 
Solution: 
Given details are, 
Principal (p) = Rs 1000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 1000 (1 + 10/100)
2
 
    = 1000 (110/100)
2
 
    = Rs 1210 
? Amount is Rs 1210 
 
5. Find the difference between the compound interest and simple interest. On a sum 
of Rs. 50,000 at 10% per annum for 2 years. 
Solution: 
Given details are, 
Principal (p) = Rs 50000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 50000 (1 + 10/100)
2
 
    = 50000 (110/100)
2
 
    = Rs 60500 
CI = Rs 60500 – 50000 = Rs 10500 
We know that SI = (PTR)/100 = (50000 × 10 × 2)/100 = Rs 10000 
? Difference amount between CI and SI = 10500 – 10000 = Rs 500 
 
6. Amit borrowed Rs. 16000 at 17 ½ % per annum simple interest. On the same day, 
he lent it to Ashu at the same rate but compounded annually. What does he gain at 
the end of 2 years? 
Solution: 
Given details are, 
Principal (p) = Rs 16000 
Rate (r) = 17 ½ % per annum = 35/2% or 17.5% 
Time (t) = 2 years 
Interest paid by Amit = (PTR)/100 = (16000×17.5×2)/100 = Rs 5600 
Amount gained by Amit: 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 16000 (1 + 17.5/100)
2
 
    = 16000 (117.5/100)
2
 
    = Rs 22090 
CI = Rs 22090 – 16000 = Rs 6090 
? Amit total gain is = Rs 6090 – 5600 = Rs 490 
 
7. Find the amount of Rs. 4096 for 18 months at 12 ½ % per annum, the interest 
being compounded semi-annually. 
Solution: 
Given details are, 
Principal (p) = Rs 4096 
Rate (r) = 12 ½ % per annum = 25/4% or 12.5/2% 
Time (t) = 18 months = (18/12) × 2 = 3 half years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 4096 (1 + 12.5/2×100)
3
 
    = 4096 (212.5/200)
3
 
    = Rs 4913 
Page 5


 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
EXERCISE 14.2                                                  PAGE NO: 14.14 
 
1. Compute the amount and the compound interest in each of the following by using 
the formulae when : 
(i) Principal = Rs 3000, Rate = 5%, Time = 2 years 
(ii) Principal = Rs 3000, Rate = 18%, Time = 2 years 
(iii) Principal = Rs 5000, Rate = 10 paise per rupee per annum, Time = 2 years 
(iv) Principal = Rs 2000, Rate = 4 paise per rupee per annum, Time = 3 years 
(v) Principal = Rs 12800, Rate = 7 ½ %, Time = 3 years 
(vi) Principal = Rs 10000, Rate = 20% per annum compounded half-yearly, Time = 
2 years 
(vii) Principal = Rs 160000, Rate = 10 paise per rupee per annum compounded half 
yearly, Time = 2 years. 
Solution: 
By using the formula, 
A = P (1 + R/100)
 n
 
Let us solve 
(i) Given, P = Rs 3000, rate = 5%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 5/100)
2
 
    = 3000 (105/100)
2
 
    = Rs 3307.5 
Compound interest (CI) = A-P = Rs 3307.5 – 3000 = Rs 307.5 
 
(ii) Given, P = Rs 3000, rate = 18%, time = 2years 
A = P (1 + R/100)
 n
 
    = 3000 (1 + 18/100)
2
 
    = 3000 (118/100)
2
 
    = Rs 4177.2 
Compound interest (CI) = A-P = Rs 4177.2 – 3000 = Rs 1177.2 
 
(iii) Given, P = Rs 5000, rate = 10%, time = 2years 
A = P (1 + R/100)
 n
 
    = 5000 (1 + 10/100)
2
 
    = 5000 (110/100)
2
 
    = Rs 6050 
Compound interest (CI) = A-P = Rs 6050 – 5000 = Rs 1050 
 
(iv) Given, P = Rs 2000, rate = 4%, time = 3years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
A = P (1 + R/100)
 n
 
    = 2000 (1 + 4/100)
3
 
    = 2000 (104/100)
3
 
    = Rs 2249.72 
Compound interest (CI) = A-P = Rs 2249.72 – 2000 = Rs 249.72 
 
(v) Given, P = Rs 12800, rate = 7 ½ % = 15/2% = 7.5%, time = 3years 
A = P (1 + R/100)
 n
 
    = 12800 (1 + 7.5/100)
3
 
    = 12800 (107.5/100)
3
 
    = Rs 15901.4 
Compound interest (CI) = A-P = Rs 15901.4 – 12800 = Rs 3101.4 
 
(vi) Given, P = Rs 10000, rate = 20 % = 20/2 = 10% (quarterly), time = 2years = 2 × 2 = 
4years 
A = P (1 + R/100)
 n
 
    = 10000 (1 + 10/100)
4
 
    = 10000 (110/100)
4
 
    = Rs 14641 
Compound interest (CI) = A-P = Rs 14641 – 10000 = Rs 4641 
 
(vii) Given, P = Rs 160000, rate = 10% = 10/2% = 5% (half yearly), time = 2years = 2×2 
= 4 quarters 
A = P (1 + R/100)
 n
 
    = 160000 (1 + 5/100)
4
 
    = 160000 (105/100)
4
 
    = Rs 194481 
Compound interest (CI) = A-P = Rs 194481 – 160000 = Rs 34481 
 
2. Find the amount of Rs. 2400 after 3 years, when the interest is compounded 
annually at the rate of 20% per annum. 
Solution: 
Given details are, 
Principal (p) = Rs 2400 
Rate (r) = 20% per annum 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 2400 (1 + 20/100)
3
 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
    = 2400 (120/100)
3
 
    = Rs 4147.2 
? Amount is Rs 4147.2 
 
3. Rahman lent Rs. 16000 to Rasheed at the rate of 12 ½ % per annum compound 
interest. Find the amount payable by Rasheed to Rahman after 3 years. 
Solution: 
Given details are, 
Principal (p) = Rs 16000 
Rate (r) = 12 ½ % per annum = 12.5% 
Time (t) = 3 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 16000 (1 + 12.5/100)
3
 
    = 16000 (112.5/100)
3
 
    = Rs 22781.25 
? Amount is Rs 22781.25 
 
4. Meera borrowed a sum of Rs. 1000 from Sita for two years. If the rate of interest 
is 10% compounded annually, find the amount that Meera has to pay back. 
Solution: 
Given details are, 
Principal (p) = Rs 1000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 1000 (1 + 10/100)
2
 
    = 1000 (110/100)
2
 
    = Rs 1210 
? Amount is Rs 1210 
 
5. Find the difference between the compound interest and simple interest. On a sum 
of Rs. 50,000 at 10% per annum for 2 years. 
Solution: 
Given details are, 
Principal (p) = Rs 50000 
Rate (r) = 10 % per annum 
Time (t) = 2 years 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 50000 (1 + 10/100)
2
 
    = 50000 (110/100)
2
 
    = Rs 60500 
CI = Rs 60500 – 50000 = Rs 10500 
We know that SI = (PTR)/100 = (50000 × 10 × 2)/100 = Rs 10000 
? Difference amount between CI and SI = 10500 – 10000 = Rs 500 
 
6. Amit borrowed Rs. 16000 at 17 ½ % per annum simple interest. On the same day, 
he lent it to Ashu at the same rate but compounded annually. What does he gain at 
the end of 2 years? 
Solution: 
Given details are, 
Principal (p) = Rs 16000 
Rate (r) = 17 ½ % per annum = 35/2% or 17.5% 
Time (t) = 2 years 
Interest paid by Amit = (PTR)/100 = (16000×17.5×2)/100 = Rs 5600 
Amount gained by Amit: 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 16000 (1 + 17.5/100)
2
 
    = 16000 (117.5/100)
2
 
    = Rs 22090 
CI = Rs 22090 – 16000 = Rs 6090 
? Amit total gain is = Rs 6090 – 5600 = Rs 490 
 
7. Find the amount of Rs. 4096 for 18 months at 12 ½ % per annum, the interest 
being compounded semi-annually. 
Solution: 
Given details are, 
Principal (p) = Rs 4096 
Rate (r) = 12 ½ % per annum = 25/4% or 12.5/2% 
Time (t) = 18 months = (18/12) × 2 = 3 half years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 4096 (1 + 12.5/2×100)
3
 
    = 4096 (212.5/200)
3
 
    = Rs 4913 
 
 
 
 
RD Sharma Solutions for Class 8 Maths Chapter 14 – 
Compound Interest 
? Amount is Rs 4913 
 
8. Find the amount and the compound interest on Rs. 8000 for 1 ½ years at 10% per 
annum, compounded half-yearly. 
Solution: 
Given details are, 
Principal (p) = Rs 8000 
Rate (r) = 10 % per annum = 10/2% = 5% (half yearly) 
Time (t) = 1 ½ years = (3/2) × 2 = 3 half years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 8000 (1 + 5/100)
3
 
    = 8000 (105/100)
3
 
    = Rs 9261 
? CI = Rs 9261 – 8000 = Rs 1261 
 
9. Kamal borrowed Rs. 57600 from LIC against her policy at 12 ½ % per annum to 
build a house. Find the amount that she pays to the LIC after 1 ½ years if the 
interest is calculated half-yearly. 
Solution: 
Given details are, 
Principal (p) = Rs 57600 
Rate (r) = 12 ½ % per annum = 25/2×2% = 25/4% = 12.5/2% (half yearly) 
Time (t) = 1 ½ years = (3/2) × 2 = 3 half years 
By using the formula, 
A = P (1 + R/100)
 n
 
    = 57600 (1 + 12.5/2×100)
3
 
    = 57600 (212.5/200)
3
 
    = Rs 69089.06 
? Amount is Rs 69089.06 
 
10. Abha purchased a house from Avas Parishad on credit. If the cost of the house is 
Rs. 64000 and the rate of interest is 5% per annum compounded half-yearly, find 
the interest paid by Abha after one year and a half. 
Solution: 
Given details are, 
Principal (p) = Rs 64000 
Rate (r) = 5 % per annum = 5/2% (half yearly) 
Time (t) = 1 ½ years = (3/2) × 2 = 3 half years 
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