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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 432 · 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. 1.88 − 9 =
  2. 2.291 + 99 =
  3. 3.65 + 9 =
  4. 4.880 − 99 =
  5. 5.76 − 19 =
  6. 6.79 + 19 =
  7. 7.22 + 9 =
  8. 8.63 − 19 =
  9. 9.33 + 9 =
  10. 10.150 + 99 =
  11. 11.67 − 29 =
  12. 12.81 − 19 =
  13. 13.642 − 99 =
  14. 14.12 + 19 =
  15. 15.61 − 19 =
  16. 16.260 + 99 =
  17. 17.26 + 19 =
  18. 18.74 − 19 =
  19. 19.27 + 19 =
  20. 20.35 + 19 =
  21. 21.39 − 29 =
  22. 22.48 − 29 =
  23. 23.17 + 19 =
  24. 24.88 − 29 =
  25. 25.39 − 19 =
  26. 26.28 + 9 =
  27. 27.77 − 19 =
  28. 28.78 − 9 =
  29. 29.72 + 9 =
  30. 30.12 + 9 =
  31. 31.28 + 19 =
  32. 32.445 + 99 =
  33. 33.798 + 99 =
  34. 34.574 − 99 =
  35. 35.92 − 19 =
  36. 36.573 + 99 =
  37. 37.725 − 99 =
  38. 38.19 + 9 =
  39. 39.70 − 29 =
  40. 40.197 + 99 =

Answer key

  1. 79
  2. 390
  3. 74
  4. 781
  5. 57
  6. 98
  7. 31
  8. 44
  9. 42
  10. 249
  11. 38
  12. 62
  13. 543
  14. 31
  15. 42
  16. 359
  17. 45
  18. 55
  19. 46
  20. 54
  21. 10
  22. 19
  23. 36
  24. 59
  25. 20
  26. 37
  27. 58
  28. 69
  29. 81
  30. 21
  31. 47
  32. 544
  33. 897
  34. 475
  35. 73
  36. 672
  37. 626
  38. 28
  39. 41
  40. 296

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