We can assume the purchase price of each item is P, and the selling price of each item is S.

The given condition is that the selling price of 30 items is equal to the purchase price of 25 items. So, we can say:

30S = 25P

Now, solve for the selling price:

S = 25/30P = 5/6 P

This means that the selling price per item is 5/6 of the purchase price

To find the profit or loss, let's first calculate the difference between the selling price and the purchase price:

Difference: P - S = P - 5/6P = 1/6 P

We know that this is a loss. 

Loss per cent: $$\dfrac{\left(\dfrac{1}{6}P\right)}{P}\times100\ =\ 16.67\%$$ Loss