Teaching points

• Teaching point 1: There are ten tens in 100; there are 100 ones in 100. 100 can also be composed multiplicatively from 50, 25 or 20, units that are commonly used in graphing and measures.
   
• Teaching point 2: Known addition facts can be used to calculate complements to 100.
   
• Teaching point 3: Known strategies for addition and subtraction across the tens boundary can be combined with unitising to count and calculate across the hundreds boundary in multiples of ten.
   
• Teaching point 4: Knowledge of two-digit numbers can be extended to count and calculate across the hundreds boundary from/to any two-digit number in ones or tens.