Estimate, Then Add or Subtract to 50
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Estimate, Then Add or Subtract to 50
Mental math for Grade 2: ten sums and differences within 50, such as 28 + 19. Estimate first, more or less than a ten near the answer, then work it out in your head. With an answer key.
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- Pages
- 1
- Last updated
- Time
- About 15 minutes
- Answer key
- Included
- Printing
- Black and white
- Related curriculum
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Estimate a sum or difference first, as more or less than a ten or as the closest ten, then work out the exact answer in your head; add and subtract 1, 10 and 100, doubles and near tens without writing the steps.
Reviewed by Ms. Olivia Parker, Teacher. How we check worksheets
How to use this sheet
- Let the child answer aloud before writing. Mental math is about the thinking, not the pencil.
- Ask "How did you do it?" after a few answers, and share another way to do the same one.
- Encourage jumps to a friendly number first: 38 + 5 is 38 + 2 + 3.
Common mistakes
- Trying to do the column method in their head and losing digits. Use friendly numbers instead: tens first, then ones.
- Adding the tens and forgetting the ones, so 30 + 24 becomes 50. Say both parts aloud.
- Rounding to make it easier and then forgetting to adjust back. If you added 2 to make a ten, take 2 away at the end.
