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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 801 · 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. 1.57 − 9 =
  2. 2.29 − 9 =
  3. 3.154 + 99 =
  4. 4.53 − 19 =
  5. 5.27 + 9 =
  6. 6.39 − 9 =
  7. 7.58 + 19 =
  8. 8.53 − 29 =
  9. 9.29 + 29 =
  10. 10.669 + 99 =
  11. 11.38 − 19 =
  12. 12.25 + 29 =
  13. 13.71 + 19 =
  14. 14.77 − 9 =
  15. 15.343 − 99 =
  16. 16.73 − 29 =
  17. 17.40 + 19 =
  18. 18.28 + 29 =
  19. 19.685 + 99 =
  20. 20.47 + 9 =
  21. 21.822 − 99 =
  22. 22.24 + 19 =
  23. 23.75 + 29 =
  24. 24.590 − 99 =
  25. 25.81 − 19 =
  26. 26.82 − 19 =
  27. 27.67 − 29 =
  28. 28.27 + 19 =
  29. 29.66 − 29 =
  30. 30.14 + 19 =
  31. 31.79 + 9 =
  32. 32.52 + 29 =
  33. 33.88 − 29 =
  34. 34.613 − 99 =
  35. 35.276 − 99 =
  36. 36.41 − 29 =
  37. 37.50 + 29 =
  38. 38.53 + 29 =
  39. 39.54 − 19 =
  40. 40.55 + 19 =

Answer key

  1. 48
  2. 20
  3. 253
  4. 34
  5. 36
  6. 30
  7. 77
  8. 24
  9. 58
  10. 768
  11. 19
  12. 54
  13. 90
  14. 68
  15. 244
  16. 44
  17. 59
  18. 57
  19. 784
  20. 56
  21. 723
  22. 43
  23. 104
  24. 491
  25. 62
  26. 63
  27. 38
  28. 46
  29. 37
  30. 33
  31. 88
  32. 81
  33. 59
  34. 514
  35. 177
  36. 12
  37. 79
  38. 82
  39. 35
  40. 74

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