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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 486 · 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. 1.288 − 99 =
  2. 2.313 − 99 =
  3. 3.43 − 19 =
  4. 4.333 + 99 =
  5. 5.33 − 9 =
  6. 6.75 − 29 =
  7. 7.543 + 99 =
  8. 8.30 + 9 =
  9. 9.323 + 99 =
  10. 10.76 + 9 =
  11. 11.219 + 99 =
  12. 12.635 + 99 =
  13. 13.709 + 99 =
  14. 14.72 − 29 =
  15. 15.76 + 29 =
  16. 16.45 − 19 =
  17. 17.71 + 19 =
  18. 18.17 − 9 =
  19. 19.104 − 29 =
  20. 20.23 − 19 =
  21. 21.80 − 19 =
  22. 22.19 − 9 =
  23. 23.57 − 29 =
  24. 24.42 − 29 =
  25. 25.18 + 9 =
  26. 26.77 + 19 =
  27. 27.13 + 19 =
  28. 28.25 + 19 =
  29. 29.41 − 29 =
  30. 30.75 − 9 =
  31. 31.17 + 19 =
  32. 32.756 + 99 =
  33. 33.22 + 29 =
  34. 34.273 + 99 =
  35. 35.99 − 19 =
  36. 36.64 − 19 =
  37. 37.80 + 9 =
  38. 38.69 + 9 =
  39. 39.29 + 9 =
  40. 40.22 − 9 =

Answer key

  1. 189
  2. 214
  3. 24
  4. 432
  5. 24
  6. 46
  7. 642
  8. 39
  9. 422
  10. 85
  11. 318
  12. 734
  13. 808
  14. 43
  15. 105
  16. 26
  17. 90
  18. 8
  19. 75
  20. 4
  21. 61
  22. 10
  23. 28
  24. 13
  25. 27
  26. 96
  27. 32
  28. 44
  29. 12
  30. 66
  31. 36
  32. 855
  33. 51
  34. 372
  35. 80
  36. 45
  37. 89
  38. 78
  39. 38
  40. 13

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