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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 810 · 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. 1.17 + 19 =
  2. 2.92 − 19 =
  3. 3.39 − 29 =
  4. 4.306 − 99 =
  5. 5.209 − 99 =
  6. 6.88 − 29 =
  7. 7.21 + 29 =
  8. 8.78 − 29 =
  9. 9.53 + 9 =
  10. 10.25 − 9 =
  11. 11.26 + 19 =
  12. 12.71 + 29 =
  13. 13.63 + 9 =
  14. 14.43 − 29 =
  15. 15.537 − 99 =
  16. 16.32 − 9 =
  17. 17.45 + 29 =
  18. 18.60 − 9 =
  19. 19.123 + 99 =
  20. 20.52 + 19 =
  21. 21.34 − 29 =
  22. 22.64 + 9 =
  23. 23.486 + 99 =
  24. 24.47 − 29 =
  25. 25.82 − 29 =
  26. 26.70 − 19 =
  27. 27.43 + 19 =
  28. 28.361 − 99 =
  29. 29.550 + 99 =
  30. 30.79 + 9 =
  31. 31.53 − 29 =
  32. 32.62 − 9 =
  33. 33.59 − 9 =
  34. 34.574 + 99 =
  35. 35.16 + 9 =
  36. 36.24 + 19 =
  37. 37.40 − 9 =
  38. 38.47 + 29 =
  39. 39.760 + 99 =
  40. 40.474 − 99 =

Answer key

  1. 36
  2. 73
  3. 10
  4. 207
  5. 110
  6. 59
  7. 50
  8. 49
  9. 62
  10. 16
  11. 45
  12. 100
  13. 72
  14. 14
  15. 438
  16. 23
  17. 74
  18. 51
  19. 222
  20. 71
  21. 5
  22. 73
  23. 585
  24. 18
  25. 53
  26. 51
  27. 62
  28. 262
  29. 649
  30. 88
  31. 24
  32. 53
  33. 50
  34. 673
  35. 25
  36. 43
  37. 31
  38. 76
  39. 859
  40. 375

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