HELP with calculations PLEASE

What is the final % concentration if 300mL is added to 250mL of a 1:200 solution of potassium permanganate. the answer is 0.227% (0.23%)

PLEASE GIVE ME WORKING OUT

So it doesn't matter what the chemical is in the solution. The point is, there is X amount of the other chemical where X/250 mL = 1/200. So you need to find X/550 mL.

x/250 mL = 1/200
200 x = 250 mL
x = 250 mL / 200 = 1.25
1.25/550 = 0.00227 = 0.227%.