Pen & Note Books Problem | PRMO-2019 | Question 16

Contents

Try this beautiful Problem from Algebra based on Pen & Note Books from PRMO 2019.

Pen & Note Books - PRMO 2019, Problem 16

A pen costs Rs.$13$ and a notebook costs Rs.$17$. A school spends exactly Rs.$10000$ in the year $2017 - 18$ to buy $x$ pens and $y$ notebooks such that $x$ and $y$ are as close as possible (i.e. $|x-y|$ is minimum). Next year, in $2018-19,$ the school spends a little more than Rs.$10000$ and buys $y$ pens and $x$ notebooks. How much more did the school pay?

$9$
$40$
$34$

Key Concepts

Algebra

Equation

multiplication

Check the Answer

But try the problem first...

Answer:$40$

Source

Try with Hints

First hint

Given A pen costs Rs.$13$ and a note book costs Rs.$17$

Nunber of pens $x$ and numbers of notebooks $y$

According to question

$13 x+17 y=10,000$ ..........................(1)
$17 x+13 y=10000+P$......................(2)

Where $\mathrm{P}$ is little more amount spend by school in $2018-19$.we have to find out the value of $P$.Can you find out?

Can you now finish the problem ..........

Second Hint

Adding (1) & (2)

$x+y=\frac{20,000+P}{30}$

Subtract (1) form (2)

$x-y=\frac{P}{4}$

Let $P=4 a$
$\begin{aligned} \text { So, } x+y=& \frac{20,000+4 a}{30} \ &=666+\frac{10+2 a}{15} \end{aligned}$

Therefore $a$=$10$

Can you finish the problem........

Final Step

Since $P=4 a$ $\Rightarrow P=40$

So school had to pay Rs. $40$ extra in $2018 - 2019$