S.chand publication New Learning Composite mathematics solution of class 8 Chapter 8 Percentage and Its Application Exercise 8D

 Exercise 8D

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Q1 | Ex-8D | Class 8 | S.Chand | New Learning Composite maths |Percentage and its application | myhelper

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Question 1

Find the simple interest and the amount of simple interest of

(a) Rs. 350 for 3 years at 6%

Sol :

$I=\frac{\text{PRT}}{100}=\frac{350\times 6\times 3}{100}$

=63

(b) Rs. 765 for 2 1 by 2 years at 5 1 by 3 percent

Sol :

P=765

$T=2\frac{1}{2}=\frac{5}{2}$y

$R=5\frac{1}{3}=\frac{16}{3}$%

I=?

$I=\frac{\text{PRT}}{100}=\frac{765\times \frac{16}{3}\times \frac{5}{2}}{100}$

$=\frac{765\times 16\times 5}{100\times 3\times 2}$

=102

∴Total amount of simple interest=102+765

=867

(c) Rs. 475 for 2 years 4 months at 4 and 1 by 2 percent.

Sol :

P=475

$R=4\frac{1}{2}=\frac{9}{2}$%

T=2year 4month

$=2+\frac{4}{12}$

$=2+\frac{1}{3}=\frac{7}{3}$

$I=\frac{\text{PRT}}{100}=\frac{475\times 9\times 7}{100\times 2\times 3}$

∴Amount simple interest

=48.875+475

=524.875

(d) Rs. 1900 for 20 months at 6%

Sol :

P=1900 , R=6%

$I=\frac{\text{PRT}}{100}=\frac{1900\times 6\times 5}{100\times 3}$

=190

∴Total I=190+1900=2090

(e) Rs. 7300 for April 5 to June 24 at 5%

Sol :

P=7300 , R=5%

T=5th april to 2 years $=\frac{80}{365}$years

$I=\frac{\text{PRT}}{100}=\frac{7300\times 5\times 80}{100\times 365}$

=80

∴Total I=7300+80

=7380

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Q2 | Ex-8D | Class 8 | S.Chand | New Learning Composite maths |Percentage and its application | myhelper

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Question 2

Find the rate per cent p.a. when Rs. 800 yields Rs. 80 interest in 2 years.

Sol :

$I=\frac{\text{PRT}}{100}$

or $R=\frac{100I}{\text{PT}}=\frac{100\times 80}{800\times 2}$

=5%

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Q3 | Ex-8D | Class 8 | S.Chand | New Learning Composite maths |Percentage and its application | myhelper

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Question 3

In what times Rs. 600 will yield Rs. 48 interest at 4% p.a.?

Sol :

P=600,  I=48 , R=4%

$T=\frac{I100}{PR}=\frac{48\times 100}{600\times 4}$

=2 year

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Q4 | Ex-8D | Class 8 | S.Chand | New Learning Composite maths |Percentage and its application | myhelper

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Question 4

Find what sum of money will yield Rs. 231 interest in 3 years at 7% p.a.

Sol :

I=231 , T=3 year, R=7%

⇒$I=\frac{\text{PRT}}{100}$

$P=\frac{I\times 100}{RT}$

$P=\frac{231\times 100}{3\times 7}$

=1100