"MUM IS 20 YEARS OLDER THAN ANDREW, AND 24 YEARS OLDER THAN ANNE. THE THREE AGES TOTAL 73. HOW OLD IS MUM & HOW OLD IS ANDREW?"

Evening everyone. My little boy is trying to solve this problem. He got the correct answer (39, 19 & 15) but it was by guessing enough numbers until it was correct. Obviously not the way it was supposed to be done. ? Can anyone please give me a way to explain it to him in **a way a 9 year old would understand**??

Most likely, this is not meant to be solved by actual algebra, as we would; it's even possible that guessing numbers is the expected way, at that age. Do you know what techniques the class has learned?

One way I've seen which is sort of an introduction to algebra, is to picture the three ages as strips of paper of appropriate lengths. We have one whose length is Mum's age; a second that is 20 less than that; and a third that is 24 less (and therefore 4 less than the second). Putting them together, the sum has to be 73.

So you might write Mum + (Mum - 20) + (Mum - 24) = 73, and then think about that.

Or, you might turn things inside out, and say that Andrew is 4 years older than Anne, and Mum is 24 years older than Anne, and label three strips as Ann, (Ann + 4), and (Ann + 24). Putting those together, you have three Annes, and 28 more, making a total of 73. Then think about that.

Algebra is just a way to do the same thinking using symbols instead of (imagined) objects.