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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 72 · 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. 1.75 − 29 =
  2. 2.812 − 99 =
  3. 3.37 + 9 =
  4. 4.572 + 99 =
  5. 5.18 + 19 =
  6. 6.55 + 29 =
  7. 7.35 + 19 =
  8. 8.224 − 99 =
  9. 9.244 − 99 =
  10. 10.306 + 99 =
  11. 11.76 − 9 =
  12. 12.25 − 9 =
  13. 13.247 + 99 =
  14. 14.14 + 29 =
  15. 15.77 − 19 =
  16. 16.34 + 19 =
  17. 17.67 − 19 =
  18. 18.47 − 9 =
  19. 19.35 − 19 =
  20. 20.28 − 19 =
  21. 21.71 + 29 =
  22. 22.30 − 9 =
  23. 23.80 + 19 =
  24. 24.53 − 19 =
  25. 25.511 − 99 =
  26. 26.29 − 19 =
  27. 27.78 + 29 =
  28. 28.66 − 9 =
  29. 29.57 + 29 =
  30. 30.508 + 99 =
  31. 31.138 + 99 =
  32. 32.333 − 99 =
  33. 33.40 + 19 =
  34. 34.96 − 29 =
  35. 35.50 − 19 =
  36. 36.203 − 99 =
  37. 37.80 − 9 =
  38. 38.22 + 19 =
  39. 39.61 + 19 =
  40. 40.14 + 9 =

Answer key

  1. 46
  2. 713
  3. 46
  4. 671
  5. 37
  6. 84
  7. 54
  8. 125
  9. 145
  10. 405
  11. 67
  12. 16
  13. 346
  14. 43
  15. 58
  16. 53
  17. 48
  18. 38
  19. 16
  20. 9
  21. 100
  22. 21
  23. 99
  24. 34
  25. 412
  26. 10
  27. 107
  28. 57
  29. 86
  30. 607
  31. 237
  32. 234
  33. 59
  34. 67
  35. 31
  36. 104
  37. 71
  38. 41
  39. 80
  40. 23

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