Divide 711 in the ratio 4:5

Add 4+5 (which is 9)Tell them to divide 711 by 9 (=79)Multiple 79 by both values (79 x 4):(79 x 5)Answer is 316 : 395Explain that there is a way of finding out if they are correct. This is by adding 316 and 395 - it should equal to 711. And it does.