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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 887 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.67 − 29 =
  2. 2.21 − 9 =
  3. 3.573 + 99 =
  4. 4.34 + 29 =
  5. 5.723 − 99 =
  6. 6.37 − 9 =
  7. 7.27 − 19 =
  8. 8.82 − 29 =
  9. 9.16 + 29 =
  10. 10.88 − 19 =
  11. 11.69 − 29 =
  12. 12.32 + 19 =
  13. 13.553 − 99 =
  14. 14.50 − 29 =
  15. 15.89 − 29 =
  16. 16.80 + 29 =
  17. 17.96 − 29 =
  18. 18.33 − 29 =
  19. 19.65 + 9 =
  20. 20.31 + 19 =
  21. 21.67 + 29 =
  22. 22.75 + 9 =
  23. 23.862 − 99 =
  24. 24.319 − 99 =
  25. 25.36 + 9 =
  26. 26.24 + 19 =
  27. 27.767 + 99 =
  28. 28.12 + 19 =
  29. 29.95 − 19 =
  30. 30.48 − 29 =
  31. 31.103 − 29 =
  32. 32.38 − 19 =
  33. 33.539 + 99 =
  34. 34.61 − 29 =
  35. 35.83 − 9 =
  36. 36.41 + 29 =
  37. 37.452 − 99 =
  38. 38.639 − 99 =
  39. 39.75 − 29 =
  40. 40.581 − 99 =

Answer key

  1. 38
  2. 12
  3. 672
  4. 63
  5. 624
  6. 28
  7. 8
  8. 53
  9. 45
  10. 69
  11. 40
  12. 51
  13. 454
  14. 21
  15. 60
  16. 109
  17. 67
  18. 4
  19. 74
  20. 50
  21. 96
  22. 84
  23. 763
  24. 220
  25. 45
  26. 43
  27. 866
  28. 31
  29. 76
  30. 19
  31. 74
  32. 19
  33. 638
  34. 32
  35. 74
  36. 70
  37. 353
  38. 540
  39. 46
  40. 482

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