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 $Rs.$

Kritika bought $25$ $i-$pads and $i-$phones for $Rs.\, 205000.$ She sold $80 \%$ of the $i-$pads and $12$ $i-$phones for a profit of $Rs.\, 40000.$ Each $i-$pad was marked up by $20 \%$ over cost and each $i-$phone was sold at a profit of $Rs.\, 2000.$ The remaining $i-$pads and $3$ $i-$phones could not be sold. What is Kritika's overall profit$/$loss?

Ramesh purchased a bicycle for $Rs.\,5200$ and spent $Rs.\,800$ on its repairs. He had to sell it for $Rs.\,5500.$ Find out his profit or loss percent.

By selling a book for $Rs.$ $360,20 \%$ profit was earned. What is the $CP$ of the book in $Rs.$?

A dairyman pays $Rs.\, 6.40$ per litre of milk. He adds water and sells the mixture at $Rs.\, 8$ per litre, thereby making $37.5\%$ profit. The proportion of water to milk received by the customers is

A man buys an article for $10 \%$ less than its value and sells it for $10 \%$ more than its value. His gain or loss percent is