Build a new ten
Add two-digit numbers by joining tens and ones, and explain the regrouping.
Explore this lesson →6 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- Add tens to tens and ones to ones.
- Forty-seven plus thirty-eight first makes seven tens and fifteen ones.
- Bundle ten of those ones: eight tens and five ones make 85. Bundling changes the arrangement, not the value.
Try it. Change it. Explain it.
Open the lesson to use its pictures and controls. In How it works, connect the picture to the idea. In Play & discover, change the quantities and notice what stays the same. In Your turn, answer questions and use the explanation to check your reasoning.
You can ask for help, draw on the thinking pad, or listen to the question and answer options. Progress distinguishes independent work from work completed with help.
Let’s try it →Curriculum connection
Grade 1 · 1.NBT · US Common Core
This lesson is mapped to these standards. A completed activity is practice evidence, not a claim of mastery. Content is checked against the linked official standards and its mathematical models are tested.