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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 718 · 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. 1.648 − 99 =
  2. 2.548 + 99 =
  3. 3.591 − 99 =
  4. 4.96 − 19 =
  5. 5.43 + 19 =
  6. 6.46 + 19 =
  7. 7.74 + 9 =
  8. 8.41 + 29 =
  9. 9.32 + 9 =
  10. 10.50 − 19 =
  11. 11.473 − 99 =
  12. 12.56 + 9 =
  13. 13.424 − 99 =
  14. 14.27 + 19 =
  15. 15.59 − 19 =
  16. 16.45 − 9 =
  17. 17.78 − 19 =
  18. 18.51 + 19 =
  19. 19.79 − 9 =
  20. 20.58 − 9 =
  21. 21.66 + 19 =
  22. 22.56 + 29 =
  23. 23.95 − 19 =
  24. 24.25 − 9 =
  25. 25.74 + 19 =
  26. 26.87 − 19 =
  27. 27.77 + 19 =
  28. 28.60 + 9 =
  29. 29.433 − 99 =
  30. 30.81 − 29 =
  31. 31.425 − 99 =
  32. 32.392 + 99 =
  33. 33.187 − 99 =
  34. 34.93 − 19 =
  35. 35.58 + 19 =
  36. 36.45 + 19 =
  37. 37.26 − 19 =
  38. 38.50 − 29 =
  39. 39.17 + 19 =
  40. 40.51 + 9 =

Answer key

  1. 549
  2. 647
  3. 492
  4. 77
  5. 62
  6. 65
  7. 83
  8. 70
  9. 41
  10. 31
  11. 374
  12. 65
  13. 325
  14. 46
  15. 40
  16. 36
  17. 59
  18. 70
  19. 70
  20. 49
  21. 85
  22. 85
  23. 76
  24. 16
  25. 93
  26. 68
  27. 96
  28. 69
  29. 334
  30. 52
  31. 326
  32. 491
  33. 88
  34. 74
  35. 77
  36. 64
  37. 7
  38. 21
  39. 36
  40. 60

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