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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 111 · 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. 1.85 − 19 =
  2. 2.388 + 99 =
  3. 3.56 − 9 =
  4. 4.46 − 19 =
  5. 5.56 − 29 =
  6. 6.55 + 9 =
  7. 7.35 − 19 =
  8. 8.28 + 9 =
  9. 9.37 − 19 =
  10. 10.23 + 9 =
  11. 11.82 − 29 =
  12. 12.33 + 9 =
  13. 13.76 + 29 =
  14. 14.80 − 19 =
  15. 15.26 + 29 =
  16. 16.48 + 9 =
  17. 17.40 − 29 =
  18. 18.27 + 29 =
  19. 19.12 − 9 =
  20. 20.73 + 29 =
  21. 21.82 − 19 =
  22. 22.67 − 9 =
  23. 23.70 − 19 =
  24. 24.22 − 9 =
  25. 25.57 + 9 =
  26. 26.795 − 99 =
  27. 27.63 + 9 =
  28. 28.63 − 9 =
  29. 29.71 − 19 =
  30. 30.51 − 9 =
  31. 31.14 + 9 =
  32. 32.44 + 9 =
  33. 33.70 + 19 =
  34. 34.20 + 29 =
  35. 35.25 + 29 =
  36. 36.19 − 9 =
  37. 37.149 + 99 =
  38. 38.173 − 99 =
  39. 39.34 − 9 =
  40. 40.86 − 19 =

Answer key

  1. 66
  2. 487
  3. 47
  4. 27
  5. 27
  6. 64
  7. 16
  8. 37
  9. 18
  10. 32
  11. 53
  12. 42
  13. 105
  14. 61
  15. 55
  16. 57
  17. 11
  18. 56
  19. 3
  20. 102
  21. 63
  22. 58
  23. 51
  24. 13
  25. 66
  26. 696
  27. 72
  28. 54
  29. 52
  30. 42
  31. 23
  32. 53
  33. 89
  34. 49
  35. 54
  36. 10
  37. 248
  38. 74
  39. 25
  40. 67

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