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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 649 · 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. 1.515 + 99 =
  2. 2.62 − 19 =
  3. 3.22 − 19 =
  4. 4.61 − 9 =
  5. 5.164 − 99 =
  6. 6.238 − 99 =
  7. 7.744 + 99 =
  8. 8.282 + 99 =
  9. 9.277 − 99 =
  10. 10.852 − 99 =
  11. 11.60 + 19 =
  12. 12.311 + 99 =
  13. 13.339 − 99 =
  14. 14.23 + 9 =
  15. 15.54 − 19 =
  16. 16.283 − 99 =
  17. 17.14 − 9 =
  18. 18.78 + 9 =
  19. 19.281 + 99 =
  20. 20.431 − 99 =
  21. 21.69 + 9 =
  22. 22.33 − 9 =
  23. 23.34 + 9 =
  24. 24.51 + 29 =
  25. 25.36 − 9 =
  26. 26.312 + 99 =
  27. 27.18 + 9 =
  28. 28.536 + 99 =
  29. 29.59 + 9 =
  30. 30.688 + 99 =
  31. 31.55 − 9 =
  32. 32.889 − 99 =
  33. 33.228 − 99 =
  34. 34.75 − 9 =
  35. 35.37 − 29 =
  36. 36.32 − 9 =
  37. 37.541 + 99 =
  38. 38.76 + 9 =
  39. 39.97 − 19 =
  40. 40.50 + 29 =

Answer key

  1. 614
  2. 43
  3. 3
  4. 52
  5. 65
  6. 139
  7. 843
  8. 381
  9. 178
  10. 753
  11. 79
  12. 410
  13. 240
  14. 32
  15. 35
  16. 184
  17. 5
  18. 87
  19. 380
  20. 332
  21. 78
  22. 24
  23. 43
  24. 80
  25. 27
  26. 411
  27. 27
  28. 635
  29. 68
  30. 787
  31. 46
  32. 790
  33. 129
  34. 66
  35. 8
  36. 23
  37. 640
  38. 85
  39. 78
  40. 79

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