I have a total of $ Rs. 300 $ in coins of denomination $ Rs. 1, Rs. 2 $ and $ Rs. 5 $. The number of $ Rs. 2 $ coins is 3 times the number of $ Rs. 5 $ coins. The total number of coins is 160 . How many coins of each denomination are with me?

AcademicMathematicsNCERTClass 8

Given :

The total number of coins $= 160$.

Sum total of all coins $= Rs. 300$.

Coins are in the denomination  $\ Rs. 1, \ Rs. 2,$ and $\ Rs. 5$. 

The number of $\ Rs. 2$ coins is 3 times the number of $\ Rs. 5$ coins.

To do :

We have to find the number of coins in each denomination.

Solution :

Let the number of Rs. 1 coins be $x$ and the number of Rs. 5 coins be $y$.

The number of Rs. 2 coins is 3 times the number of Rs. 5 coins.

This implies,

The number of Rs. 2 coins $= 3y$.

Therefore,

$x+3y+y=160$

$x+4y=160$.................(i)

$[x(1)+3y(2)+y(5)] = Rs. 300$

$x+6y+5y=300$

$x+11y=300$..................(ii)

Subtract equation (i) from equation (ii).

$(x+11y)-(x+4y)=300-160$

$x-x+11y-4y=140$

$7y=140$

$y=\frac{140}{7}$

$y=20$

Substituting $y=20$ in equation (i),

$x+4y=160$

$x+4(20)=160$

$x+80=160$

$x=160-80$

$x=80$

$y=20$

$\Rightarrow 3y=3(20)$

$=60$

Therefore,

The number of Rs. 1 coins is 80, Rs. 2 coins is 60, and Rs. 5 coins is 20.

raja
Updated on 10-Oct-2022 13:47:38

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