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Simple Interest RD Sharma Solutions | Mathematics (Maths) Class 7 PDF Download

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 Page 1


 
 
1. Find the simple interest, when:
(i) Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
(ii) Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years.
(iii) Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months.
(iv) Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months.
(v) Principal = Rs 1000, Rate of Interest = 10% per annum and Time = 73 days.
Solution: 
(i) Given Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (2000 × 5 × 5)/100
= Rs 500
(ii) Given Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years. 
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (500 × 4 × 12.5)/100
= Rs 250
(iii) Given Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months = 
½ years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (4500 × ½ × 4)/100
SI = (4500 × 1 × 4)/100 × 2
= Rs 90
(iv) Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months 
= (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
Page 2


 
 
1. Find the simple interest, when:
(i) Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
(ii) Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years.
(iii) Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months.
(iv) Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months.
(v) Principal = Rs 1000, Rate of Interest = 10% per annum and Time = 73 days.
Solution: 
(i) Given Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (2000 × 5 × 5)/100
= Rs 500
(ii) Given Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years. 
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (500 × 4 × 12.5)/100
= Rs 250
(iii) Given Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months = 
½ years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (4500 × ½ × 4)/100
SI = (4500 × 1 × 4)/100 × 2
= Rs 90
(iv) Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months 
= (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
 
 
= Rs 720 
(v) Given Principal = Rs 1000, Rate of Interest = 10% per annum and
Time = 73 days = (73/365) days
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (1000 × (73/365) × 10)/100
SI = (1000 × 73 × 10)/100 × 365
= Rs 20
2. Find the interest on Rs 500 for a period of 4 years at the rate of 8% per annum. Also,
find the amount to be paid at the end of the period.
Solution: 
Given Principal amount P = Rs 500 
Time period T = 4 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (500 × 4 × 8)/100 
= Rs 160 
Amount = Principal amount + Interest  
= Rs 500 + 160 
= Rs 660 
3. A sum of Rs 400 is lent at the rate of 5% per annum. Find the interest at the end of 2
years.
Solution: 
Given Principal amount P = Rs 400 
Time period T = 2 years 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 2 × 5)/100 
= Rs 40 
Page 3


 
 
1. Find the simple interest, when:
(i) Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
(ii) Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years.
(iii) Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months.
(iv) Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months.
(v) Principal = Rs 1000, Rate of Interest = 10% per annum and Time = 73 days.
Solution: 
(i) Given Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (2000 × 5 × 5)/100
= Rs 500
(ii) Given Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years. 
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (500 × 4 × 12.5)/100
= Rs 250
(iii) Given Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months = 
½ years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (4500 × ½ × 4)/100
SI = (4500 × 1 × 4)/100 × 2
= Rs 90
(iv) Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months 
= (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
 
 
= Rs 720 
(v) Given Principal = Rs 1000, Rate of Interest = 10% per annum and
Time = 73 days = (73/365) days
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (1000 × (73/365) × 10)/100
SI = (1000 × 73 × 10)/100 × 365
= Rs 20
2. Find the interest on Rs 500 for a period of 4 years at the rate of 8% per annum. Also,
find the amount to be paid at the end of the period.
Solution: 
Given Principal amount P = Rs 500 
Time period T = 4 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (500 × 4 × 8)/100 
= Rs 160 
Amount = Principal amount + Interest  
= Rs 500 + 160 
= Rs 660 
3. A sum of Rs 400 is lent at the rate of 5% per annum. Find the interest at the end of 2
years.
Solution: 
Given Principal amount P = Rs 400 
Time period T = 2 years 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 2 × 5)/100 
= Rs 40 
 
 
4. A sum of Rs 400 is lent for 3 years at the rate of 6% per annum. Find the interest.
Solution: 
Principal amount P = Rs 400 
Time period T = 3 years 
Rate of interest R = 6% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 3 × 6)/100 
= Rs 72 
5. A person deposits Rs 25000 in a firm who pays an interest at the rate of 20% per
annum. Calculate the income he gets from it annually.
Solution: 
Given Principal amount P = Rs 25000 
Time period T = 1 year 
Rate of interest R = 20% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (25000 × 1 × 20)/100 
= Rs 5000 
6. A man borrowed Rs 8000 from a bank at 8% per annum. Find the amount he has to
pay after 4 ½ years.
Solution: 
Given Principal amount P = Rs 8000 
Time period T = 4 ½ years = 9/2 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (8000 × (9/2) × 8)/100 
= Rs 2880 
Amount = Principal amount + Interest  
= Rs 8000 + 2880 
= Rs 10880 
Page 4


 
 
1. Find the simple interest, when:
(i) Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
(ii) Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years.
(iii) Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months.
(iv) Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months.
(v) Principal = Rs 1000, Rate of Interest = 10% per annum and Time = 73 days.
Solution: 
(i) Given Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (2000 × 5 × 5)/100
= Rs 500
(ii) Given Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years. 
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (500 × 4 × 12.5)/100
= Rs 250
(iii) Given Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months = 
½ years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (4500 × ½ × 4)/100
SI = (4500 × 1 × 4)/100 × 2
= Rs 90
(iv) Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months 
= (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
 
 
= Rs 720 
(v) Given Principal = Rs 1000, Rate of Interest = 10% per annum and
Time = 73 days = (73/365) days
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (1000 × (73/365) × 10)/100
SI = (1000 × 73 × 10)/100 × 365
= Rs 20
2. Find the interest on Rs 500 for a period of 4 years at the rate of 8% per annum. Also,
find the amount to be paid at the end of the period.
Solution: 
Given Principal amount P = Rs 500 
Time period T = 4 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (500 × 4 × 8)/100 
= Rs 160 
Amount = Principal amount + Interest  
= Rs 500 + 160 
= Rs 660 
3. A sum of Rs 400 is lent at the rate of 5% per annum. Find the interest at the end of 2
years.
Solution: 
Given Principal amount P = Rs 400 
Time period T = 2 years 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 2 × 5)/100 
= Rs 40 
 
 
4. A sum of Rs 400 is lent for 3 years at the rate of 6% per annum. Find the interest.
Solution: 
Principal amount P = Rs 400 
Time period T = 3 years 
Rate of interest R = 6% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 3 × 6)/100 
= Rs 72 
5. A person deposits Rs 25000 in a firm who pays an interest at the rate of 20% per
annum. Calculate the income he gets from it annually.
Solution: 
Given Principal amount P = Rs 25000 
Time period T = 1 year 
Rate of interest R = 20% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (25000 × 1 × 20)/100 
= Rs 5000 
6. A man borrowed Rs 8000 from a bank at 8% per annum. Find the amount he has to
pay after 4 ½ years.
Solution: 
Given Principal amount P = Rs 8000 
Time period T = 4 ½ years = 9/2 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (8000 × (9/2) × 8)/100 
= Rs 2880 
Amount = Principal amount + Interest  
= Rs 8000 + 2880 
= Rs 10880 
 
 
7. Rakesh lent out Rs 8000 for 5 years at 15% per annum and borrowed Rs 6000 for 3
years at 12% per annum. How much did he gain or lose?
Solution: 
Given Principal amount P = Rs 8000 
Time period T = 5 years 
Rate of interest R = 15% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (8000 × 5 × 15)/100 
= Rs 6000 
Principal amount P = Rs 6000 
Time period T = 3 years 
Rate of interest R = 12% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (6000 × 3 × 12)/100 
= Rs 2160 
Amount gained by Rakesh = Rs 6000 - Rs 2160  
= Rs 3840 
8. Anita deposits Rs 1000 in a savings bank account. The bank pays interest at the rate
of 5% per annum. What amount can Anita get after one year?
Solution: 
Given Principal amount P = Rs 1000 
Time period T = 1 year 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (1000 × 1 × 5)/100 
= Rs 50 
Total amount paid after 1 year = Principal amount + Interest 
= Rs 1000 + Rs 50 
= Rs 1050 
9. Nalini borrowed Rs 550 from her friend at 8% per annum. She returned the amount
Page 5


 
 
1. Find the simple interest, when:
(i) Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
(ii) Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years.
(iii) Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months.
(iv) Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months.
(v) Principal = Rs 1000, Rate of Interest = 10% per annum and Time = 73 days.
Solution: 
(i) Given Principal = Rs 2000, Rate of Interest = 5% per annum and Time = 5 years.
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (2000 × 5 × 5)/100
= Rs 500
(ii) Given Principal = Rs 500, Rate of Interest = 12.5% per annum and Time = 4 years. 
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (500 × 4 × 12.5)/100
= Rs 250
(iii) Given Principal = Rs 4500, Rate of Interest = 4% per annum and Time = 6 months = 
½ years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (4500 × ½ × 4)/100
SI = (4500 × 1 × 4)/100 × 2
= Rs 90
(iv) Given Principal = Rs 12000, Rate of Interest = 18% per annum and Time = 4 months 
= (4/12) = (1/3) years
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (12000 × (1/3) × 18)/100
SI = (12000 × 1 × 18)/100 × 3
 
 
= Rs 720 
(v) Given Principal = Rs 1000, Rate of Interest = 10% per annum and
Time = 73 days = (73/365) days
We know that simple interest = (P × T × R)/100
On substituting these values in above equation we get
SI = (1000 × (73/365) × 10)/100
SI = (1000 × 73 × 10)/100 × 365
= Rs 20
2. Find the interest on Rs 500 for a period of 4 years at the rate of 8% per annum. Also,
find the amount to be paid at the end of the period.
Solution: 
Given Principal amount P = Rs 500 
Time period T = 4 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (500 × 4 × 8)/100 
= Rs 160 
Amount = Principal amount + Interest  
= Rs 500 + 160 
= Rs 660 
3. A sum of Rs 400 is lent at the rate of 5% per annum. Find the interest at the end of 2
years.
Solution: 
Given Principal amount P = Rs 400 
Time period T = 2 years 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 2 × 5)/100 
= Rs 40 
 
 
4. A sum of Rs 400 is lent for 3 years at the rate of 6% per annum. Find the interest.
Solution: 
Principal amount P = Rs 400 
Time period T = 3 years 
Rate of interest R = 6% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (400 × 3 × 6)/100 
= Rs 72 
5. A person deposits Rs 25000 in a firm who pays an interest at the rate of 20% per
annum. Calculate the income he gets from it annually.
Solution: 
Given Principal amount P = Rs 25000 
Time period T = 1 year 
Rate of interest R = 20% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (25000 × 1 × 20)/100 
= Rs 5000 
6. A man borrowed Rs 8000 from a bank at 8% per annum. Find the amount he has to
pay after 4 ½ years.
Solution: 
Given Principal amount P = Rs 8000 
Time period T = 4 ½ years = 9/2 years 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (8000 × (9/2) × 8)/100 
= Rs 2880 
Amount = Principal amount + Interest  
= Rs 8000 + 2880 
= Rs 10880 
 
 
7. Rakesh lent out Rs 8000 for 5 years at 15% per annum and borrowed Rs 6000 for 3
years at 12% per annum. How much did he gain or lose?
Solution: 
Given Principal amount P = Rs 8000 
Time period T = 5 years 
Rate of interest R = 15% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (8000 × 5 × 15)/100 
= Rs 6000 
Principal amount P = Rs 6000 
Time period T = 3 years 
Rate of interest R = 12% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (6000 × 3 × 12)/100 
= Rs 2160 
Amount gained by Rakesh = Rs 6000 - Rs 2160  
= Rs 3840 
8. Anita deposits Rs 1000 in a savings bank account. The bank pays interest at the rate
of 5% per annum. What amount can Anita get after one year?
Solution: 
Given Principal amount P = Rs 1000 
Time period T = 1 year 
Rate of interest R = 5% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (1000 × 1 × 5)/100 
= Rs 50 
Total amount paid after 1 year = Principal amount + Interest 
= Rs 1000 + Rs 50 
= Rs 1050 
9. Nalini borrowed Rs 550 from her friend at 8% per annum. She returned the amount
 
 
after 6 months. How much did she pay? 
Solution: 
Given Principal amount P = Rs 550 
Time period T = ½ year 
Rate of interest R = 8% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (550 × ½ × 8)/100 
= Rs 22 
Total amount paid after ½ year = Principal amount + Interest 
= Rs 550 + Rs 22 
= Rs 572 
10. Rohit borrowed Rs 60000 from a bank at 9% per annum for 2 years. He lent this 
sum of money to Rohan at 10% per annum for 2 years. How much did Rohit earn from 
this transaction?
Solution: 
Given Principal amount P = Rs 60000 
Time period T = 2 years 
Rate of interest R = 10% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (60000 × 2 × 10)/100 
= Rs 12000 
Principal amount P = Rs 60000 
Time period T = 2 years 
Rate of interest R = 9% p.a. 
We know that simple interest = (P × T × R)/100 
On substituting these values in above equation we get 
SI = (60000 × 2 × 9)/100 
= Rs 10800 
Amount gained by Rohit = Rs 12000 - Rs 10800 
= Rs 1200 
11. Romesh borrowed Rs 2000 at 2% per annum and Rs 1000 at 5% per annum. He
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