$P$ invests $Rs.\, 9100$ for $3\, months.$ $Q$ invests $Rs.\, 6825$ for $2\, months$ and $R$ $Rs.\, 8190$ for $5\, months$ in a business. If the total profit amounts to $Rs.$ $4158,$ how much profit should $Q$ get? (in $Rs.$)

Surbhi bought a combined total of $25$ i-pads and i-phones. She marked up the i-pad by $20 \%$ on the cost price, while each i-phone was marked up by $Rs.\, 2000.$ She was able to sell $75 \%$ of the i-pads and $2$ i-phones and make a profit of $Rs.$ $49000 .$ The remaining i-pads and $3$ i-phones could not be sold by her. Find her overall profit or loss if she gets no return on unsold items and it is known that an i-phone costs $50 \%$ of an i-pad.

If the cost price of $12$ pens is equal to selling price of $8$ pens, find the gain percent.

Albert buys $4$ $horses$ and $9$ cows for $Rs. 13400$. If he sells the horse at $10 \%$ profit and the cows at $20 \%$ profit, then he earns a total profit of $Rs.\, 1880 .$ The cost of a horse is (in $Rs.$)

Find $CP$ when $SP = Rs.\, 51 .70, \operatorname{loss}=12 \% ?$

A discount series of $10 \%, 20 \%$ and $40 \%$ is equal to a single discount of.......$\%$