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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 943 · 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. 1.37 − 9 =
  2. 2.72 + 29 =
  3. 3.80 − 19 =
  4. 4.14 + 19 =
  5. 5.24 − 9 =
  6. 6.54 − 19 =
  7. 7.56 + 19 =
  8. 8.56 − 19 =
  9. 9.28 + 19 =
  10. 10.16 + 9 =
  11. 11.55 + 9 =
  12. 12.756 − 99 =
  13. 13.340 − 99 =
  14. 14.97 − 19 =
  15. 15.69 − 19 =
  16. 16.76 + 9 =
  17. 17.73 − 9 =
  18. 18.71 + 9 =
  19. 19.46 + 19 =
  20. 20.76 − 29 =
  21. 21.774 + 99 =
  22. 22.37 + 9 =
  23. 23.36 + 19 =
  24. 24.596 − 99 =
  25. 25.38 − 9 =
  26. 26.84 − 9 =
  27. 27.15 + 9 =
  28. 28.66 + 19 =
  29. 29.93 − 19 =
  30. 30.226 − 99 =
  31. 31.332 + 99 =
  32. 32.32 − 19 =
  33. 33.92 − 29 =
  34. 34.13 − 9 =
  35. 35.64 − 29 =
  36. 36.53 + 19 =
  37. 37.46 − 19 =
  38. 38.73 − 19 =
  39. 39.220 + 99 =
  40. 40.92 − 19 =

Answer key

  1. 28
  2. 101
  3. 61
  4. 33
  5. 15
  6. 35
  7. 75
  8. 37
  9. 47
  10. 25
  11. 64
  12. 657
  13. 241
  14. 78
  15. 50
  16. 85
  17. 64
  18. 80
  19. 65
  20. 47
  21. 873
  22. 46
  23. 55
  24. 497
  25. 29
  26. 75
  27. 24
  28. 85
  29. 74
  30. 127
  31. 431
  32. 13
  33. 63
  34. 4
  35. 35
  36. 72
  37. 27
  38. 54
  39. 319
  40. 73

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