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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 732 · 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. 1.70 − 29 =
  2. 2.80 + 9 =
  3. 3.54 − 9 =
  4. 4.53 + 19 =
  5. 5.20 + 9 =
  6. 6.598 − 99 =
  7. 7.65 + 9 =
  8. 8.41 + 9 =
  9. 9.316 + 99 =
  10. 10.48 − 9 =
  11. 11.25 + 19 =
  12. 12.378 + 99 =
  13. 13.35 − 9 =
  14. 14.413 − 99 =
  15. 15.187 + 99 =
  16. 16.23 + 29 =
  17. 17.17 + 9 =
  18. 18.650 + 99 =
  19. 19.703 − 99 =
  20. 20.87 − 9 =
  21. 21.35 + 19 =
  22. 22.63 − 9 =
  23. 23.46 + 9 =
  24. 24.22 + 19 =
  25. 25.96 − 19 =
  26. 26.31 − 9 =
  27. 27.23 − 9 =
  28. 28.55 + 9 =
  29. 29.74 − 9 =
  30. 30.40 + 19 =
  31. 31.308 + 99 =
  32. 32.71 − 29 =
  33. 33.630 − 99 =
  34. 34.12 − 9 =
  35. 35.21 + 19 =
  36. 36.35 + 9 =
  37. 37.74 + 19 =
  38. 38.174 + 99 =
  39. 39.76 + 19 =
  40. 40.34 − 19 =

Answer key

  1. 41
  2. 89
  3. 45
  4. 72
  5. 29
  6. 499
  7. 74
  8. 50
  9. 415
  10. 39
  11. 44
  12. 477
  13. 26
  14. 314
  15. 286
  16. 52
  17. 26
  18. 749
  19. 604
  20. 78
  21. 54
  22. 54
  23. 55
  24. 41
  25. 77
  26. 22
  27. 14
  28. 64
  29. 65
  30. 59
  31. 407
  32. 42
  33. 531
  34. 3
  35. 40
  36. 44
  37. 93
  38. 273
  39. 95
  40. 15

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