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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 768 · 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. 1.45 − 29 =
  2. 2.27 − 19 =
  3. 3.44 + 19 =
  4. 4.518 + 99 =
  5. 5.573 + 99 =
  6. 6.77 − 19 =
  7. 7.52 + 9 =
  8. 8.39 + 9 =
  9. 9.16 − 9 =
  10. 10.28 + 29 =
  11. 11.189 − 99 =
  12. 12.38 + 19 =
  13. 13.280 − 99 =
  14. 14.71 − 19 =
  15. 15.180 − 99 =
  16. 16.25 + 19 =
  17. 17.41 + 19 =
  18. 18.45 − 9 =
  19. 19.17 − 9 =
  20. 20.86 − 29 =
  21. 21.35 − 9 =
  22. 22.217 + 99 =
  23. 23.19 − 9 =
  24. 24.207 + 99 =
  25. 25.58 + 29 =
  26. 26.38 − 9 =
  27. 27.54 − 19 =
  28. 28.17 + 29 =
  29. 29.578 + 99 =
  30. 30.308 + 99 =
  31. 31.250 − 99 =
  32. 32.16 + 19 =
  33. 33.36 − 29 =
  34. 34.201 − 99 =
  35. 35.68 − 9 =
  36. 36.53 − 29 =
  37. 37.605 − 99 =
  38. 38.32 + 19 =
  39. 39.50 + 19 =
  40. 40.29 + 29 =

Answer key

  1. 16
  2. 8
  3. 63
  4. 617
  5. 672
  6. 58
  7. 61
  8. 48
  9. 7
  10. 57
  11. 90
  12. 57
  13. 181
  14. 52
  15. 81
  16. 44
  17. 60
  18. 36
  19. 8
  20. 57
  21. 26
  22. 316
  23. 10
  24. 306
  25. 87
  26. 29
  27. 35
  28. 46
  29. 677
  30. 407
  31. 151
  32. 35
  33. 7
  34. 102
  35. 59
  36. 24
  37. 506
  38. 51
  39. 69
  40. 58

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