Some articles were bought at $6$ for $Rs. 5$ and sold at $5$ for $Rs. 6 .$ Gain percent is

$10 \%$ discount and then $20 \%$ discount in succession is equivalent to total discount of.......$\%$

A shopkeeper professes to sell his goods at cost price but uses a weight of $800\, g$ instead of kilogram weight. Thus, he makes a profit of

A trader purchase a wrist watch and a pendulum for $Rs.$ $390.$ He sells them making a profit of $10 \%$ on the watch and $15 \%$ on the pendulum. He earns a profit of $Rs$. $51.50 .$ The difference between the original prices of the pendulum and the watch is equal to? (in $Rs.$)

At a cost of $60$ paise per article, Sarika produces $750$ articles. She puts the selling price such that if only $600$ articles are sold, she would have made a profit of $40 \%$ on the outlay. However, $120$ articles got spoilt and she was able to sell $630$ articles at this price. Find her actual profit or loss percent as the percentage of total outlay assuming that the unsold articles are useless.

$X$ sells two articles for $Rs.\, 4,000$ each with no loss and no gain in the interaction. If one was sold at a gain of $25 \%$ the other is sold at a loss of........$\%$