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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 86 · 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. 1.44 − 19 =
  2. 2.75 − 9 =
  3. 3.529 + 99 =
  4. 4.28 + 19 =
  5. 5.35 + 19 =
  6. 6.38 + 19 =
  7. 7.59 + 19 =
  8. 8.53 + 29 =
  9. 9.630 + 99 =
  10. 10.67 + 29 =
  11. 11.53 − 29 =
  12. 12.500 − 99 =
  13. 13.12 + 19 =
  14. 14.397 − 99 =
  15. 15.57 − 9 =
  16. 16.56 + 19 =
  17. 17.75 + 19 =
  18. 18.67 + 19 =
  19. 19.24 + 19 =
  20. 20.583 + 99 =
  21. 21.50 + 19 =
  22. 22.80 + 19 =
  23. 23.46 + 29 =
  24. 24.72 + 9 =
  25. 25.273 − 99 =
  26. 26.76 + 9 =
  27. 27.78 + 29 =
  28. 28.84 − 9 =
  29. 29.565 − 99 =
  30. 30.71 − 19 =
  31. 31.27 + 9 =
  32. 32.36 − 29 =
  33. 33.173 + 99 =
  34. 34.63 − 9 =
  35. 35.72 − 19 =
  36. 36.32 + 29 =
  37. 37.93 − 19 =
  38. 38.36 + 19 =
  39. 39.74 + 19 =
  40. 40.180 + 99 =

Answer key

  1. 25
  2. 66
  3. 628
  4. 47
  5. 54
  6. 57
  7. 78
  8. 82
  9. 729
  10. 96
  11. 24
  12. 401
  13. 31
  14. 298
  15. 48
  16. 75
  17. 94
  18. 86
  19. 43
  20. 682
  21. 69
  22. 99
  23. 75
  24. 81
  25. 174
  26. 85
  27. 107
  28. 75
  29. 466
  30. 52
  31. 36
  32. 7
  33. 272
  34. 54
  35. 53
  36. 61
  37. 74
  38. 55
  39. 93
  40. 279

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