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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 655 · 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. 1.238 + 99 =
  2. 2.46 − 19 =
  3. 3.319 − 99 =
  4. 4.476 − 99 =
  5. 5.48 + 19 =
  6. 6.450 + 99 =
  7. 7.14 + 19 =
  8. 8.71 + 9 =
  9. 9.31 + 29 =
  10. 10.68 + 19 =
  11. 11.80 − 19 =
  12. 12.27 + 19 =
  13. 13.86 − 19 =
  14. 14.35 + 19 =
  15. 15.44 + 9 =
  16. 16.509 − 99 =
  17. 17.503 + 99 =
  18. 18.423 + 99 =
  19. 19.26 − 9 =
  20. 20.94 − 29 =
  21. 21.42 − 19 =
  22. 22.746 + 99 =
  23. 23.62 + 29 =
  24. 24.465 + 99 =
  25. 25.818 − 99 =
  26. 26.31 + 9 =
  27. 27.47 + 29 =
  28. 28.45 + 9 =
  29. 29.40 + 29 =
  30. 30.57 + 9 =
  31. 31.79 + 19 =
  32. 32.44 − 19 =
  33. 33.55 + 9 =
  34. 34.25 + 19 =
  35. 35.13 + 19 =
  36. 36.73 + 19 =
  37. 37.24 − 9 =
  38. 38.38 + 9 =
  39. 39.63 + 9 =
  40. 40.253 + 99 =

Answer key

  1. 337
  2. 27
  3. 220
  4. 377
  5. 67
  6. 549
  7. 33
  8. 80
  9. 60
  10. 87
  11. 61
  12. 46
  13. 67
  14. 54
  15. 53
  16. 410
  17. 602
  18. 522
  19. 17
  20. 65
  21. 23
  22. 845
  23. 91
  24. 564
  25. 719
  26. 40
  27. 76
  28. 54
  29. 69
  30. 66
  31. 98
  32. 25
  33. 64
  34. 44
  35. 32
  36. 92
  37. 15
  38. 47
  39. 72
  40. 352

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