An abacus is an excellent resource for helping your child understand 2-digit numbers up to 99. It shows clearly the two columns, the ones and the tens. In other words the 2 yellow balls in the tens column have a value of 20 whilst the two balls in the ones column have a value of 2. This will also help later when multiplying by 10 as they can see each digit moving one place to the left.

Using bar models to help make number sentences correct. Use of < > and =.

Using part whole models with 2-digit numbers.