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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 143 · 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. 1.392 + 99 =
  2. 2.326 + 99 =
  3. 3.65 − 19 =
  4. 4.447 − 99 =
  5. 5.70 − 19 =
  6. 6.25 + 9 =
  7. 7.31 + 29 =
  8. 8.188 − 99 =
  9. 9.49 + 19 =
  10. 10.95 − 19 =
  11. 11.22 + 19 =
  12. 12.67 − 19 =
  13. 13.65 + 9 =
  14. 14.638 − 99 =
  15. 15.48 − 19 =
  16. 16.248 + 99 =
  17. 17.45 + 9 =
  18. 18.60 + 9 =
  19. 19.525 + 99 =
  20. 20.277 + 99 =
  21. 21.20 + 9 =
  22. 22.719 − 99 =
  23. 23.33 − 9 =
  24. 24.183 − 99 =
  25. 25.24 − 19 =
  26. 26.85 − 9 =
  27. 27.79 + 19 =
  28. 28.78 − 9 =
  29. 29.47 − 9 =
  30. 30.47 + 19 =
  31. 31.35 − 29 =
  32. 32.54 − 9 =
  33. 33.30 − 9 =
  34. 34.50 + 9 =
  35. 35.79 − 9 =
  36. 36.36 − 29 =
  37. 37.53 − 9 =
  38. 38.493 + 99 =
  39. 39.43 − 19 =
  40. 40.900 − 99 =

Answer key

  1. 491
  2. 425
  3. 46
  4. 348
  5. 51
  6. 34
  7. 60
  8. 89
  9. 68
  10. 76
  11. 41
  12. 48
  13. 74
  14. 539
  15. 29
  16. 347
  17. 54
  18. 69
  19. 624
  20. 376
  21. 29
  22. 620
  23. 24
  24. 84
  25. 5
  26. 76
  27. 98
  28. 69
  29. 38
  30. 66
  31. 6
  32. 45
  33. 21
  34. 59
  35. 70
  36. 7
  37. 44
  38. 592
  39. 24
  40. 801

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