This game is about place value and adding, subtracting and also using tidy numbers.

I found this easy because 100 cm is 1 metre. My question was "How many metres is 305 cm?". Well 300cm is 3 metres and 5 cm is not counted as a metre. I didn't find this hard to figure out. Next I would want to learn about BEDMAS.

http://www.amblesideprimary.com/ambleweb/mentalmaths/mentalmachine2.html