first, add up the parts of the ratio... 2+3+5=10 then divide the whole into individual parts... 25/10=2.5 then multiply the value of 1 part by the amount in the ratio... 2.5 x 2 =5 2.5 x 3 = 7.5 2.5 x 5 = 12.5 so the final ratio is 5kg:7.5kg:12.5kg Hope this helps :)