Work out a fresh calculation
Find exact sums and differences, then check your method.
Explore this lesson →12 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- Choose a sound method and keep each operand's place values clear.
- A general written method works through the columns while accounting for every carried or exchanged unit.
- Use subtraction to check a sum, or addition to check a difference.
- A correct final number is useful numerical evidence. It does not by itself show which written method was used.
- Accuracy and increasing ease across fresh problems and later days build fluency; there is no timer here.
Something to notice
Let the learner work on paper or the scribble pad before opening help. Observe the method and ask about a carry or exchange. The app scores only the submitted number in this family, so it does not certify the handwriting, method choice or long-term fluency. Try fresh calculations again later.
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 4 · 4.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.