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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 731 · 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. 1.12 + 9 =
  2. 2.36 − 9 =
  3. 3.53 − 29 =
  4. 4.42 − 29 =
  5. 5.623 + 99 =
  6. 6.55 + 9 =
  7. 7.45 − 29 =
  8. 8.87 − 9 =
  9. 9.48 − 19 =
  10. 10.61 + 9 =
  11. 11.68 − 29 =
  12. 12.216 + 99 =
  13. 13.650 − 99 =
  14. 14.48 + 9 =
  15. 15.82 − 9 =
  16. 16.589 + 99 =
  17. 17.422 + 99 =
  18. 18.35 + 9 =
  19. 19.719 + 99 =
  20. 20.37 − 19 =
  21. 21.56 + 9 =
  22. 22.367 + 99 =
  23. 23.671 + 99 =
  24. 24.75 − 9 =
  25. 25.689 + 99 =
  26. 26.76 − 19 =
  27. 27.524 + 99 =
  28. 28.12 + 19 =
  29. 29.100 − 29 =
  30. 30.31 + 19 =
  31. 31.63 + 9 =
  32. 32.51 − 9 =
  33. 33.175 + 99 =
  34. 34.70 + 19 =
  35. 35.884 − 99 =
  36. 36.745 + 99 =
  37. 37.26 + 29 =
  38. 38.72 + 9 =
  39. 39.60 + 19 =
  40. 40.14 − 9 =

Answer key

  1. 21
  2. 27
  3. 24
  4. 13
  5. 722
  6. 64
  7. 16
  8. 78
  9. 29
  10. 70
  11. 39
  12. 315
  13. 551
  14. 57
  15. 73
  16. 688
  17. 521
  18. 44
  19. 818
  20. 18
  21. 65
  22. 466
  23. 770
  24. 66
  25. 788
  26. 57
  27. 623
  28. 31
  29. 71
  30. 50
  31. 72
  32. 42
  33. 274
  34. 89
  35. 785
  36. 844
  37. 55
  38. 81
  39. 79
  40. 5

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