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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 153 · 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. 1.54 − 29 =
  2. 2.35 − 9 =
  3. 3.55 − 29 =
  4. 4.422 + 99 =
  5. 5.18 − 9 =
  6. 6.22 − 19 =
  7. 7.100 − 29 =
  8. 8.59 − 9 =
  9. 9.59 − 19 =
  10. 10.64 − 29 =
  11. 11.18 + 29 =
  12. 12.107 − 29 =
  13. 13.28 + 9 =
  14. 14.36 + 9 =
  15. 15.71 + 9 =
  16. 16.31 + 19 =
  17. 17.269 + 99 =
  18. 18.353 − 99 =
  19. 19.590 − 99 =
  20. 20.42 + 29 =
  21. 21.14 − 9 =
  22. 22.432 − 99 =
  23. 23.60 + 29 =
  24. 24.279 + 99 =
  25. 25.40 − 29 =
  26. 26.315 − 99 =
  27. 27.29 + 29 =
  28. 28.75 + 29 =
  29. 29.156 + 99 =
  30. 30.703 − 99 =
  31. 31.43 + 9 =
  32. 32.228 − 99 =
  33. 33.35 + 9 =
  34. 34.68 − 29 =
  35. 35.27 − 9 =
  36. 36.153 + 99 =
  37. 37.50 − 9 =
  38. 38.58 − 19 =
  39. 39.348 − 99 =
  40. 40.182 + 99 =

Answer key

  1. 25
  2. 26
  3. 26
  4. 521
  5. 9
  6. 3
  7. 71
  8. 50
  9. 40
  10. 35
  11. 47
  12. 78
  13. 37
  14. 45
  15. 80
  16. 50
  17. 368
  18. 254
  19. 491
  20. 71
  21. 5
  22. 333
  23. 89
  24. 378
  25. 11
  26. 216
  27. 58
  28. 104
  29. 255
  30. 604
  31. 52
  32. 129
  33. 44
  34. 39
  35. 18
  36. 252
  37. 41
  38. 39
  39. 249
  40. 281

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