What actually happens
"Add a nought" gets the right answer and teaches the wrong thing. What happens is that every digit moves one place to the left: the 7 that meant seven now means seventy, and the nought is there to hold the empty units place. Said that way, the rule still works in two years' time when the numbers have decimal points in them and adding a nought has stopped being true.
It carries three other tables
The 5 table is this one halved. The 9 table is this one with one lot taken off. The hardest steps in the 7 and 8 tables are reached by starting here and stepping back. A child who is fast and certain on the 10 table has a place to stand for everything else, which is why it is worth practising even when it looks too easy.
Dividing by ten
The divide round is the part of this page worth doing. 80 รท 10 is the same move backwards, and a child who is fluent forwards is often slow backwards. That gap is the whole reason the game asks both.