Two successive discounts of $4 \%$ on any item are equivalent to a single discount of $\%$

By selling $90$ pens for $Rs. 80$,a man loses $20\%$. What should be the selling price (in $Rs.$) of $90$ pens for $20\%$ profit?

$A$ white goods dealer pays $10 \%$ custom duty on an iPhone that costs $Rs. 25000$ in $UK$. For how much should he mark it,if he desires to make a profit of $20 \%$ after giving a discount of $25 \%$ to the buyer? (in $Rs$)

If a discount of $10 \%$ is given on the marked price of a radio,the gain is $20 \%$. If the discount is increased to $20 \%$,the gain is......$\%$

Vijay sold a watch at a gain of $5 \%$. Had he sold it for $Rs. 72$ more,he would have gained $13 \%$. Find out the cost price of the watch (in $Rs.$).

$A$ cloth merchant says that due to a slump in the market,he sells cloth at a $10 \%$ loss,but he uses an inaccurate metre scale and actually gains $15 \%$. Find out the actual length of the scale (in $cm$).