Add double-digit numbers by combining tens, combining ones, and then adding the partial sums. This module reinforces the skills of using expanded form, the Make 10s and Make 20 strategies, and adding multiples of 10, in order to add 2-digit numbers with and without regrouping.
Transition from ten frames to using Base 10 blocks to unitize and model numbers in units of ten and one. What's 83? 80 and 3. It's also 8 tens and 3 ones. To know there are 8 tens, add 5 tens and 3 tens. To encourage Base 10 thinking, use both formal names and nicknames. 83 is both "eighty-three" and "8 ten 3." Prerequisites: 1-96 ○ 1-90
Add 2-digit and 1-digit numbers with no regrouping. First add the ones, then add back the tens to get the total. What's 26+2? Since 6+2 = 8 and 20+8 = 28, 26+2 = 28. Start by modeling numbers with concrete Base 10 Blocks or snap cubes. Progress to using pictorial number bonds and finally, just mental math. Prerequisites: 1-49
Generalize the Make 10 strategy to the Make 20 strategy. Continue using ten frames to model the parts and total. What's 18 + 6? Break 6 into 2 parts. First make 20, then add the rest. Since 6 = 2 + 4, add 18 + 2 = 20, then add 20 + 4 = 24. Encourage students to think in groups of 10 whenever possible. Prerequisites: 1-45
