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Grade 1 · lesson 3 of 4

Add a Multiple of Ten

Count the starting tens and the added tens.

About 15 minutes, plus any extended practice

Download the grade pack

Supplied materials

  • Paper and a pencil; drawing and spoken explanations are welcome. An adult may read directions and options aloud.
  • Supplied worked-case record: For 24+30, two tens and four ones receive three more tens.
  • All quantities and shape descriptions are supplied in the worked example and questions; no purchase or personal information is needed.

Learn the idea

A multiple of ten adds full tens and no extra ones. Combine the tens groups and keep the existing ones. This uses place value rather than counting every individual object. Check that the whole sum remains within the stated number range.

Count the starting tens and the added tens. Add those group counts, then keep the starting ones. Write the new two-digit total and explain why the ones have not changed.

Read thirty as three tens, not three ones. Adding full tens does not change the ones count. Write the number of tens beneath each addend and keep its ones visible.

  1. Write the number of tens beneath each addend and keep its ones visible.
  2. Follow the worked example. Point to each number or shape feature and say what it tells you.
  3. Count the starting tens and the added tens.
  4. Try the question and then the three practice questions. Check your answers and explain any change you make.
Worked example

See the method in action

For 24+30, two tens and four ones receive three more tens. Five tens and four ones make 54. The four single ones were not changed. Adding only three would give 27, so the three added groups must each represent ten. Read thirty as three tens, not three ones. Adding full tens does not change the ones count. Write the number of tens beneath each addend and keep its ones visible.

Your turn

Check your reasoning

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Helpful tips
  • Read thirty as three tens, not three ones.
  • Adding full tens does not change the ones count.
Find 22+20 by adding full tens.

Feedback appears here after you check. This is practice, not a graded school assessment.

See the answer and explanation

42

Add the tens while preserving the original ones. The result is 42.

Take it further

Find 35+40. Expected: seven tens and five ones, or 75.

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More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. Find 23+30 by adding full tens.
Need a hint?
  • Read thirty as three tens, not three ones.
  • Adding full tens does not change the ones count.
2. Find 24+40 by adding full tens.
Need a hint?
  • Read thirty as three tens, not three ones.
  • Adding full tens does not change the ones count.
3. Find 25+50 by adding full tens.
Need a hint?
  • Read thirty as three tens, not three ones.
  • Adding full tens does not change the ones count.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

Check the subject sources

These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.