You're assuming that the relationship is linear, and it isn't. It would be like assuming that 1/3 is exactly midway between 1/2 and 1/4, but of course 4/12 is not halfway between 6/12 and 3/12.Can someone tell me why I'm wrong here please.
100 / 15 = 6.7
But when I worked it out in my head I did it like this:
100/10 = 10
100/20 = 5
therefore 100/15 = 7.5
why is it wrong when I do it like that?