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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 530 · 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. 1.316 − 99 =
  2. 2.32 − 29 =
  3. 3.80 − 19 =
  4. 4.353 − 99 =
  5. 5.24 + 9 =
  6. 6.25 + 29 =
  7. 7.475 − 99 =
  8. 8.43 + 19 =
  9. 9.63 + 9 =
  10. 10.60 + 19 =
  11. 11.220 + 99 =
  12. 12.27 + 29 =
  13. 13.140 + 99 =
  14. 14.85 − 9 =
  15. 15.27 − 9 =
  16. 16.71 + 9 =
  17. 17.296 − 99 =
  18. 18.80 + 29 =
  19. 19.269 + 99 =
  20. 20.54 + 19 =
  21. 21.77 − 19 =
  22. 22.50 + 9 =
  23. 23.31 + 29 =
  24. 24.26 − 19 =
  25. 25.44 + 19 =
  26. 26.255 + 99 =
  27. 27.48 + 19 =
  28. 28.79 − 9 =
  29. 29.51 + 19 =
  30. 30.49 + 9 =
  31. 31.77 − 29 =
  32. 32.74 − 19 =
  33. 33.459 − 99 =
  34. 34.76 + 9 =
  35. 35.36 − 19 =
  36. 36.63 + 19 =
  37. 37.22 − 19 =
  38. 38.26 + 9 =
  39. 39.231 + 99 =
  40. 40.79 + 29 =

Answer key

  1. 217
  2. 3
  3. 61
  4. 254
  5. 33
  6. 54
  7. 376
  8. 62
  9. 72
  10. 79
  11. 319
  12. 56
  13. 239
  14. 76
  15. 18
  16. 80
  17. 197
  18. 109
  19. 368
  20. 73
  21. 58
  22. 59
  23. 60
  24. 7
  25. 63
  26. 354
  27. 67
  28. 70
  29. 70
  30. 58
  31. 48
  32. 55
  33. 360
  34. 85
  35. 17
  36. 82
  37. 3
  38. 35
  39. 330
  40. 108

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