The cost price of $40$ articles is the same as the selling price of $25$ articles. Find the gain percent. (in $\%$)

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

$A$ vendor started selling vegetables at $Rs. 10$ per $kg$,but could not find buyers at this rate. So,he reduced the price to $Rs. 8.10$ per $kg$,but uses a faulty weight of $900\, g$ for $1\, kg$. Find the percent change in the actual price or loss. (in $\%$)

$A$ man sold his two horses for $Rs. 770$ each. On one he gained $10\%$ and on the other he lost $10\%$. The average gain or loss percentage is:

$A$ retailer offers the following discount schemes for buyers on an article:
$I.$ Two successive discounts of $10 \%$
$II.$ $A$ discount of $12 \%$ followed by a discount of $8 \%$
$III.$ Successive discounts of $15 \%$ and $5 \%$
$IV.$ $A$ discount of $20 \%$
The selling price will be minimum under the scheme:

Sardar Singh bought $200$ dozen oranges at $Rs. 10$ a dozen. He spent $₹500$ on transportation. He sold them at $Rs. 1$ each. What was his profit or loss percent?