Students use the clues provided to systematically eliminate numbers from a 1-100 grid. This is ideal for high ability students in Grades 6-8. I have previously set it as a homework task for my top set Year 7s (equivalent to Grade 6 in America). It can be given out as an activity to do in class, but be warned - it could take them anywhere between 30 minutes to 1 hour to complete.
The clues are all about factors, multiples and primes. Note: a few clues also refer to HCF (Highest Common Factor) and LCM (Lowest Common Multiple). The file is possible to edit if your terminology differs slightly.
"I am not a factor of 36"
"I am not a prime number between 30 and 50"
"I am not a multiple of 13"
"I am not 46 or 69, nor am I their HCF"
The answer to each clue is provided (i.e a full list of numbers which should be eliminated with that clue) as well as the final number which should be remaining at the end.
I always emphasise to my class the need to work through the clues from top to bottom (to avoid too many numbers being eliminated too quickly). If they work from top to bottom they will eliminate only a handful at a time.
Please leave your feedback! I would love to know if your students enjoy this task as much as mine have!