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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 582 · 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. 1.48 + 29 =
  2. 2.57 − 9 =
  3. 3.36 − 29 =
  4. 4.156 − 99 =
  5. 5.38 + 19 =
  6. 6.25 − 19 =
  7. 7.34 − 29 =
  8. 8.529 + 99 =
  9. 9.15 + 9 =
  10. 10.26 + 19 =
  11. 11.39 − 9 =
  12. 12.251 − 99 =
  13. 13.34 − 9 =
  14. 14.21 + 29 =
  15. 15.19 − 9 =
  16. 16.169 − 99 =
  17. 17.55 + 9 =
  18. 18.598 + 99 =
  19. 19.242 + 99 =
  20. 20.42 + 19 =
  21. 21.14 − 9 =
  22. 22.74 + 9 =
  23. 23.179 + 99 =
  24. 24.53 − 9 =
  25. 25.95 − 29 =
  26. 26.18 + 19 =
  27. 27.78 + 29 =
  28. 28.74 − 9 =
  29. 29.50 − 19 =
  30. 30.16 − 9 =
  31. 31.67 − 19 =
  32. 32.40 + 19 =
  33. 33.78 + 9 =
  34. 34.23 + 9 =
  35. 35.80 + 29 =
  36. 36.24 + 19 =
  37. 37.48 − 29 =
  38. 38.32 + 9 =
  39. 39.456 + 99 =
  40. 40.253 − 99 =

Answer key

  1. 77
  2. 48
  3. 7
  4. 57
  5. 57
  6. 6
  7. 5
  8. 628
  9. 24
  10. 45
  11. 30
  12. 152
  13. 25
  14. 50
  15. 10
  16. 70
  17. 64
  18. 697
  19. 341
  20. 61
  21. 5
  22. 83
  23. 278
  24. 44
  25. 66
  26. 37
  27. 107
  28. 65
  29. 31
  30. 7
  31. 48
  32. 59
  33. 87
  34. 32
  35. 109
  36. 43
  37. 19
  38. 41
  39. 555
  40. 154

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