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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 630 · 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. 1.17 + 9 =
  2. 2.20 + 9 =
  3. 3.18 + 19 =
  4. 4.177 + 99 =
  5. 5.862 − 99 =
  6. 6.27 + 29 =
  7. 7.62 − 19 =
  8. 8.83 − 19 =
  9. 9.54 + 9 =
  10. 10.44 − 29 =
  11. 11.52 + 9 =
  12. 12.13 + 9 =
  13. 13.54 + 19 =
  14. 14.84 − 9 =
  15. 15.76 + 9 =
  16. 16.22 − 9 =
  17. 17.59 − 19 =
  18. 18.36 − 9 =
  19. 19.67 + 9 =
  20. 20.785 − 99 =
  21. 21.285 + 99 =
  22. 22.34 − 19 =
  23. 23.13 − 9 =
  24. 24.45 + 19 =
  25. 25.14 + 19 =
  26. 26.374 − 99 =
  27. 27.44 + 29 =
  28. 28.87 − 29 =
  29. 29.50 − 9 =
  30. 30.59 + 29 =
  31. 31.76 + 19 =
  32. 32.61 + 29 =
  33. 33.30 − 9 =
  34. 34.54 − 19 =
  35. 35.394 − 99 =
  36. 36.98 − 29 =
  37. 37.618 − 99 =
  38. 38.18 − 9 =
  39. 39.51 − 19 =
  40. 40.23 − 9 =

Answer key

  1. 26
  2. 29
  3. 37
  4. 276
  5. 763
  6. 56
  7. 43
  8. 64
  9. 63
  10. 15
  11. 61
  12. 22
  13. 73
  14. 75
  15. 85
  16. 13
  17. 40
  18. 27
  19. 76
  20. 686
  21. 384
  22. 15
  23. 4
  24. 64
  25. 33
  26. 275
  27. 73
  28. 58
  29. 41
  30. 88
  31. 95
  32. 90
  33. 21
  34. 35
  35. 295
  36. 69
  37. 519
  38. 9
  39. 32
  40. 14

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