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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 616 · 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. 1.401 + 99 =
  2. 2.38 + 9 =
  3. 3.35 − 19 =
  4. 4.421 + 99 =
  5. 5.71 + 9 =
  6. 6.97 − 29 =
  7. 7.19 + 19 =
  8. 8.52 + 9 =
  9. 9.50 + 29 =
  10. 10.24 + 9 =
  11. 11.760 + 99 =
  12. 12.80 + 29 =
  13. 13.18 − 9 =
  14. 14.29 + 29 =
  15. 15.57 − 9 =
  16. 16.565 + 99 =
  17. 17.55 − 19 =
  18. 18.53 − 19 =
  19. 19.24 + 19 =
  20. 20.386 − 99 =
  21. 21.34 + 19 =
  22. 22.28 − 9 =
  23. 23.674 − 99 =
  24. 24.38 + 29 =
  25. 25.676 + 99 =
  26. 26.51 + 9 =
  27. 27.71 + 19 =
  28. 28.75 + 9 =
  29. 29.23 + 19 =
  30. 30.50 + 9 =
  31. 31.46 − 19 =
  32. 32.432 − 99 =
  33. 33.62 + 9 =
  34. 34.38 − 9 =
  35. 35.65 + 9 =
  36. 36.98 − 29 =
  37. 37.61 + 19 =
  38. 38.224 + 99 =
  39. 39.103 − 29 =
  40. 40.616 − 99 =

Answer key

  1. 500
  2. 47
  3. 16
  4. 520
  5. 80
  6. 68
  7. 38
  8. 61
  9. 79
  10. 33
  11. 859
  12. 109
  13. 9
  14. 58
  15. 48
  16. 664
  17. 36
  18. 34
  19. 43
  20. 287
  21. 53
  22. 19
  23. 575
  24. 67
  25. 775
  26. 60
  27. 90
  28. 84
  29. 42
  30. 59
  31. 27
  32. 333
  33. 71
  34. 29
  35. 74
  36. 69
  37. 80
  38. 323
  39. 74
  40. 517

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