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A man has certain notes of …

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A man has certain notes of denominations Rs. 20 and Rs. 5 which amount to Rs. 380. If the number of notes of each kind is interchanged, they amount to Rs. 60 less as before. Find the number of notes of each denomination.
  • 1 answers

Preeti Dabral 1 year, 8 months ago

Let’s consider the number of 20 rupee notes to be x
And the number of 5 rupee notes be y

Then, according to the given conditions, we have

20x+5y=380     … (i) and

5x+20y=380−60

⇒5x+20y=320     … (ii)

Now, multiplying eq(i) by 4 and subtracting with eq(ii), we get

(80x+20y)−(5x+20y)=1520−320

⇒75x=1200

{tex}\begin{aligned} & \Rightarrow \mathrm{x}=\frac{1200}{75} \\ & \Rightarrow \mathrm{x}=16 \end{aligned}{/tex}

On substituting the value of x in eq(i), we get

20(16)+5y=380

⇒320+5y=380

⇒5y=380−320=60

{tex}\begin{aligned} & \Rightarrow y=\frac{60}{5} \\ & \Rightarrow y=12 \end{aligned}{/tex}

Therefore, 

The number of 20 rupee notes =16 and 

The number of 5 rupee notes =12

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