Question

a lady went to a bank with Rs. 1lakhs . she asked the casher to give her Rs. 5 hundred & Rs. 1 thousand currency notes in return . she got 175 currency notes in all . find the number of each kind of currency notes .

Answer 1

Dear student,
$$\begin{gathered} LetthenumberofRs500notesbe\text{'}x\text{'} \\ andthenumberofRs1000notesbe\text{'}y\text{'} \\ Acc.toquestion, \\ x+y=175---\left[1\right] \\ Multiply\left[1\right]by500weget \\ 500x+500y=87500--\left[2\right] \\ 500x+1000y=100000--\left[3\right] \\ solving\left[2\right]and\left[3\right] \\ 500x+500y=87500 \\ 500x+1000y=100000 \\ \underline{---} \\ -500y=-12500 \\ \Rightarrow y=\frac{-12500}{-500} \\ \Rightarrow \boxed{y=25} \\ from\left[1\right] \\ x+25=175 \\ \Rightarrow x=175-25 \\ \Rightarrow \boxed{x=150} \\ thustheno.ofRs500notes=150 \\ theno.ofRs1000notes=25 \end{gathered}$$
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