Hello all,

I will appreciate if someone can help me regarding the following question. This is from CSSE 2017 entry Maths paper.

Q. Two square numbers have a difference of 33. Identify the two missing numbers that complete this calculations.
square(A) - square(B) = 33
fill in the two empty boxes to show our answer:
square(__) - square(__) = 33

My son gave us the following answer
square(17) - square(16) = 33

But the answer given at the end of the CSSE paper is as below -
square(7) - square(4) = 33

As you can see both the answers are correct. I just wanted check how would the checker treat this, if there are multiple answers possible and some of these are not mentioned on the answer sheet?

This is a case where those setting the exam have not been careful enough - clearly there are two possible answers but they weren't expecting 10-year olds to know any square numbers other than 1-12, and were presumably expecting them to discover the answer by trial and error.

Well done to your son - has he spotted the pattern that pairs of adjacent square numbers always differ by successive odd numbers? He will go far with that kind of mathematical insight - a useful lesson that sometimes there is more than one "right" answer

Many thanks for your kind reply

You've hit the nail on the head there. Knowledge of square numbers up to 12 should be taken as a given at 11+ level. Going on speed of calculations, trial and improvement within numbers 1-12 is what's required here.