A man sells a scooter to his friend at $10 \%$ loss. If the friend sells it for $RS.\, 4000$ and gains $20\%,$ find out the original cost price of the scooter. (in $Rs.$)

A man purchased $150$ pens at the rate of $Rs.\, 12$ per pen. He sold 50 pens at gain of $10 \% .$ The percentage gain at which he must sell the remaining pens so as to gain $15 \%$ on the whole outlay is........$\%$

A man purchases some oranges at the rate of $3$ for $Rs.\,40$ and the same quantity at $5$ for $Rs.\, 60.$ If he sells all the oranges at the rate of $3$ for $Rs.\, 50,$ find his gain or loss percent (to the nearest integer).

A cab driver makes a profit of $20 \%$ on every trip when he carries $3$ passengers and the price of petrol is $Rs.\,30$ a litre. Find the percentage profit for the same journey if he goes with four passengers per trip and the price of petrol reduces to $Rs.\, 24$ a litre? (in $\%$)

(Assume that revenue per passenger is the same in both the cases.)

If the cost price of an item is $\frac{2}{5}$ of its marked price and if it is sold at a discount of $10 \%,$ then there will be

Find $SP$ when $CP = Rs.\; 80 .40, \operatorname{loss}=5 \% ?$