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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 967 · 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. 1.39 − 19 =
  2. 2.275 + 99 =
  3. 3.68 − 9 =
  4. 4.55 + 29 =
  5. 5.78 − 29 =
  6. 6.80 − 9 =
  7. 7.592 − 99 =
  8. 8.38 + 19 =
  9. 9.23 + 9 =
  10. 10.24 + 19 =
  11. 11.44 − 19 =
  12. 12.14 + 19 =
  13. 13.27 + 9 =
  14. 14.44 + 19 =
  15. 15.93 − 29 =
  16. 16.54 − 29 =
  17. 17.36 + 9 =
  18. 18.20 − 9 =
  19. 19.24 + 9 =
  20. 20.50 − 9 =
  21. 21.26 − 9 =
  22. 22.41 + 29 =
  23. 23.687 + 99 =
  24. 24.501 + 99 =
  25. 25.12 + 9 =
  26. 26.491 − 99 =
  27. 27.49 − 9 =
  28. 28.656 + 99 =
  29. 29.752 + 99 =
  30. 30.77 + 9 =
  31. 31.38 + 29 =
  32. 32.33 − 9 =
  33. 33.51 − 19 =
  34. 34.53 − 9 =
  35. 35.75 + 9 =
  36. 36.60 − 19 =
  37. 37.74 + 19 =
  38. 38.251 − 99 =
  39. 39.38 + 9 =
  40. 40.34 + 9 =

Answer key

  1. 20
  2. 374
  3. 59
  4. 84
  5. 49
  6. 71
  7. 493
  8. 57
  9. 32
  10. 43
  11. 25
  12. 33
  13. 36
  14. 63
  15. 64
  16. 25
  17. 45
  18. 11
  19. 33
  20. 41
  21. 17
  22. 70
  23. 786
  24. 600
  25. 21
  26. 392
  27. 40
  28. 755
  29. 851
  30. 86
  31. 67
  32. 24
  33. 32
  34. 44
  35. 84
  36. 41
  37. 93
  38. 152
  39. 47
  40. 43

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