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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 201 · 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. 1.530 + 99 =
  2. 2.735 − 99 =
  3. 3.781 − 99 =
  4. 4.79 − 19 =
  5. 5.697 − 99 =
  6. 6.49 − 29 =
  7. 7.793 + 99 =
  8. 8.892 − 99 =
  9. 9.349 − 99 =
  10. 10.52 − 19 =
  11. 11.97 − 19 =
  12. 12.58 − 19 =
  13. 13.84 − 19 =
  14. 14.769 + 99 =
  15. 15.12 + 19 =
  16. 16.670 + 99 =
  17. 17.25 + 9 =
  18. 18.64 − 19 =
  19. 19.170 − 99 =
  20. 20.23 + 19 =
  21. 21.15 − 9 =
  22. 22.63 − 9 =
  23. 23.79 − 29 =
  24. 24.55 + 9 =
  25. 25.22 + 19 =
  26. 26.283 + 99 =
  27. 27.15 + 9 =
  28. 28.57 + 9 =
  29. 29.51 + 9 =
  30. 30.22 + 9 =
  31. 31.21 + 19 =
  32. 32.92 − 29 =
  33. 33.416 − 99 =
  34. 34.51 + 29 =
  35. 35.399 + 99 =
  36. 36.791 − 99 =
  37. 37.38 + 19 =
  38. 38.233 − 99 =
  39. 39.53 + 29 =
  40. 40.31 − 9 =

Answer key

  1. 629
  2. 636
  3. 682
  4. 60
  5. 598
  6. 20
  7. 892
  8. 793
  9. 250
  10. 33
  11. 78
  12. 39
  13. 65
  14. 868
  15. 31
  16. 769
  17. 34
  18. 45
  19. 71
  20. 42
  21. 6
  22. 54
  23. 50
  24. 64
  25. 41
  26. 382
  27. 24
  28. 66
  29. 60
  30. 31
  31. 40
  32. 63
  33. 317
  34. 80
  35. 498
  36. 692
  37. 57
  38. 134
  39. 82
  40. 22

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