Digits, divisibility and integer structure
Build a model, justify why it applies and check the result.
IKMC Grades 9-10 - Selected Topics
Write a number in expanded place-value form, such as $\overline{abc}=100a+10b+c$ with $a\ne 0$.
Use prime factorisation to compare divisibility and to find a GCD or an LCM.
Use parity (odd and even) as an invariant when a process allows only certain moves.
Count the trailing zeros of a product by pairing factors 2 and 5.