By selling 25 metres of cloth, a trader gains the selling price of 5 metres of cloth. The gain of the trader in percentage isa.20%b.29%c.28%d.25%

The gain of the trader can be calculated using the formula for profit percentage which is (Profit/Cost Price) * 100.

Here, the profit is the selling price of 5 metres of cloth.

The cost price is the cost of 25 metres of cloth (since that's what the trader sold to make the profit).

But since the profit is given in terms of the selling price of the cloth, we can say that the selling price of 25 metres of cloth is equal to the cost price of 25 metres of cloth plus the selling price of 5 metres of cloth (which is the profit).

So, the cost price of 25 metres of cloth is the selling price of 25 metres of cloth minus the selling price of 5 metres of cloth.

Let's assume the selling price of 1 metre of cloth is $1.

Then, the selling price of 25 metres of cloth is $25 and the selling price of 5 metres of cloth (the profit) is$5.

So, the cost price of 25 metres of cloth is $25 -$5 = $20.

Now, we can calculate the profit percentage as (Profit/Cost Price) * 100 = ($5/$20) * 100 = 25%.

So, the gain of the trader in percentage is 25% (option d).