It is not the only question in that section that does not have a unique solution. There are three different possible answers to the question about the teacher with n cards.
Thank you smouse, jared25 & pulse876. Sorry for the delay in replying - I headed off to bed after posting it - Hubby in hospital and I had had a long day - I didn't understand the question - never mind the answer so thanks go to you all and Ben of course (again)
This is the answer that he gave me for the teacher question
Bearing in mind every number is the square number of something( but we won�t get
into that I�ll assume the question asks for the squares of integers only)(and
yes I do enjoy being pedantic)
n=25 25 cards, 25 is 5� and so the cards have the squares of 1 2 3 4 and 5 25
cards 5 square numbers and so one fifth of the cards are square numbers.
I agree that 25 is a possible answer to the card question. But the teacher could also have 15 cards (which would contain the three square numbers 1, 4 and 9) or 20 cards (which would contain the four square numbers 1, 4, 9 and 16). The question doesn't specify that n itself must be a square number, only effectively that it must be divisible by five.
granny g - in the same section did you or he get an answer to the question requiring you to insert mathematical sign(s) to make the sum correct?
If so, did you/he:
(a) use different mathematical signs in different gaps (which is relatively easy to solve), or
(b) use the same mathematical sign in each of the gaps (which a strict reading of the question would suggest is required) which is far more difficult and has me stumped.
You never know smouse - you seem to be on a roll. I've just had my second prize for the Retford Lions Quiz delivered - nice bottle of Bushmills. One of the Lions has a daughter who lives near by so it arrived safe and sound. It will be a nice welcome home pressie for my husband.