A merchant buys $4000\, kg$ of wheat, one$-$fifth of which he sells at a gain of $5$ per cent, one$-$fourth at a gain of $10 \%$, one-half at a gain of $12$ percent, and the remainder at a gain of $16$ percent. If he had sold the whole at a gain of $11$ percent, he would have made $Rs.\, 72.80$ more. What was the cost price of the crop per kg? (in $Rs.$)

If eggs are bought $12$ for $Rs.\, 10$ and sold at $10$ for $Rs.\, 12$. What is the gain or loss $\%.$

Half of $100$ articles were sold at a profit of $20 \%$ and the rest at a profit of $40 \% .$ If all of the articles had been sold at a profit of $25 \%,$ the total profit would have been $Rs.\,100$ less than earlier profit. The cost price of each article was (in $Rs.$)

Suresh buys a camera for $Rs.\,1800$ and sells it at $10 \%$ loss. Find out its selling price. (in $Rs.$)

In these questions, two equations mabered $I$ and $II$ are given. You have to solve both the equations and mark the appropriate option.

$I.$ $2 x^{2}-11 x+15=0$

$II$. $2 y^{2}-11 y+14=0$

An article is sold for $Rs.\,4950$ at a gain of $10 \% .$ What would have been the gain or loss per cent if it had been sold for $Rs$ $4275 ?$