- Home
- Standard 13
- Quantitative Aptitude
Ravipurchases $90$ pens and sells $40$ pens at a gain of $10 \%$ and $50$ pens at a gain of $20 \% .$ Had he sold all of them at a uniform profit of $15 \%$ he would have got $Rs.\, 40$ less. Find the cost price of each pen in $Rs.$
$80$
$75$
$90$
$100$
Solution
Let the $CP$ of each pen be $Rs. 100$
At the profit of $10 \%,$ $SP$ of $40$ pens $=(100+10) \times 40=$ $Rs. 4400$
At the profit of $20 \%,$ $SP$ of $50$ pens $=(100+20) \times 50=$ $Rs. 6000$
$SP$ of $90$ pens $=$ Rs. $(4400+6000)=$ $Rs. 10400$
$CP$ of $90$ pens $=$ $Rs.$ $(90 \times 100)=$ $Rs. 9000$
At the profit of $15 \%,$ $SP$ of $90$ pens $=$ $Rs.$ $(90 \times 115)=$ $Rs. 10350$
Difference in $SP =$ $Rs.$ $(10400-10350)=$ $Rs. 50$
If the difference is Rs. $50,$ then $C P=R s .100$
If the difference is Rs. $40,$ then $CP$
$=\frac{100 \times 40}{50}=$ $Rs. 80$
Hence, the cost price of each pen is $Rs. 80$