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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 1 · 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. 1.127 + 99 =
  2. 2.59 − 9 =
  3. 3.85 − 19 =
  4. 4.49 + 19 =
  5. 5.236 + 99 =
  6. 6.81 − 19 =
  7. 7.20 + 19 =
  8. 8.726 + 99 =
  9. 9.89 − 19 =
  10. 10.75 + 9 =
  11. 11.20 + 9 =
  12. 12.35 + 19 =
  13. 13.81 − 29 =
  14. 14.728 + 99 =
  15. 15.25 + 19 =
  16. 16.81 − 9 =
  17. 17.150 + 99 =
  18. 18.48 + 19 =
  19. 19.89 − 9 =
  20. 20.50 − 29 =
  21. 21.35 + 29 =
  22. 22.20 + 29 =
  23. 23.94 − 19 =
  24. 24.77 + 9 =
  25. 25.31 − 9 =
  26. 26.254 − 99 =
  27. 27.61 + 19 =
  28. 28.43 + 29 =
  29. 29.419 + 99 =
  30. 30.52 + 9 =
  31. 31.48 − 9 =
  32. 32.57 − 9 =
  33. 33.711 − 99 =
  34. 34.334 + 99 =
  35. 35.776 + 99 =
  36. 36.42 − 29 =
  37. 37.72 + 9 =
  38. 38.62 + 9 =
  39. 39.329 − 99 =
  40. 40.74 + 19 =

Answer key

  1. 226
  2. 50
  3. 66
  4. 68
  5. 335
  6. 62
  7. 39
  8. 825
  9. 70
  10. 84
  11. 29
  12. 54
  13. 52
  14. 827
  15. 44
  16. 72
  17. 249
  18. 67
  19. 80
  20. 21
  21. 64
  22. 49
  23. 75
  24. 86
  25. 22
  26. 155
  27. 80
  28. 72
  29. 518
  30. 61
  31. 39
  32. 48
  33. 612
  34. 433
  35. 875
  36. 13
  37. 81
  38. 71
  39. 230
  40. 93

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