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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 113 · 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. 1.33 − 29 =
  2. 2.15 − 9 =
  3. 3.47 − 19 =
  4. 4.619 − 99 =
  5. 5.817 − 99 =
  6. 6.427 + 99 =
  7. 7.322 − 99 =
  8. 8.44 + 9 =
  9. 9.31 + 29 =
  10. 10.76 + 29 =
  11. 11.65 − 19 =
  12. 12.90 − 29 =
  13. 13.332 − 99 =
  14. 14.71 + 29 =
  15. 15.98 − 29 =
  16. 16.60 − 19 =
  17. 17.33 − 9 =
  18. 18.69 + 19 =
  19. 19.64 − 9 =
  20. 20.413 + 99 =
  21. 21.310 + 99 =
  22. 22.625 − 99 =
  23. 23.45 − 9 =
  24. 24.42 − 9 =
  25. 25.45 + 19 =
  26. 26.695 + 99 =
  27. 27.694 + 99 =
  28. 28.64 + 9 =
  29. 29.80 + 9 =
  30. 30.16 + 9 =
  31. 31.42 + 19 =
  32. 32.380 + 99 =
  33. 33.35 + 29 =
  34. 34.12 + 9 =
  35. 35.26 − 9 =
  36. 36.313 + 99 =
  37. 37.51 + 19 =
  38. 38.69 − 29 =
  39. 39.65 + 19 =
  40. 40.40 + 29 =

Answer key

  1. 4
  2. 6
  3. 28
  4. 520
  5. 718
  6. 526
  7. 223
  8. 53
  9. 60
  10. 105
  11. 46
  12. 61
  13. 233
  14. 100
  15. 69
  16. 41
  17. 24
  18. 88
  19. 55
  20. 512
  21. 409
  22. 526
  23. 36
  24. 33
  25. 64
  26. 794
  27. 793
  28. 73
  29. 89
  30. 25
  31. 61
  32. 479
  33. 64
  34. 21
  35. 17
  36. 412
  37. 70
  38. 40
  39. 84
  40. 69

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