In other words, they never memorized their multiplication tables! Many times I have seen a student do poorly due to a weakness in basic math facts they should have learned in third grade.
As a middle-school math teacher, I have seen many students who do understand abstract concepts, and even enjoy learning about things like Pi and the Pythagorean Theorem, but who appear to be unable to do so due to a weak grasp of math fundamentals.
How much money do I have left if I buy a soda? By the end of the week, how much of my daily allowance will I be able to save if I don't?
Subtract 1-, 2-, 3-, 4-, or 5-digit number from a 5-digit number