Here's some good math jokes, as nominated by teachers and Twitter.
sheepdog gets all the sheep in the pen for his farmer. He comes back
and says ‘All 40 accounted for.’ Farmer says, ‘I’ve only got 36!’
Sheepdog replies, ‘I know, but I rounded them up.'
Two cats called '1,2,3' & 'un,deux,trois' had swim race across channel.
1,2,3 cat won because un, deux, trois cat sank!
Followed by seven brilliant runners-up:
Hired an odd-job man to do 8 jobs for me. When I got back, he'd only done jobs 1,3,5, and 7
Have you heard about the mathematical plant? It has square roots
After careful investigation, it was found that aliens' heights were paranormally distributed
I hit someone with a scientific calculator - I used the cosh button
What kind of tree could a maths teacher climb? = Geometry
What do you get if you cross a maths teacher and a clock? Arithma-ticks!
Last night I dreamed that I was weightless! I was like, 0mg