Thomas from Beechwood Park School didn't stop at the blocks with J on them:
Chloe and Georgia from Moorgate CP School, and Matt from St Andrew's School also calculated carefully.
Class 5 from Spring Grove Primary School in Hounslow told us:
These numbers are called triangle numbers because you would be able to arrange the number of blocks into a triangle formation. It would also work if they were counters as well.
That's right! Thank you.