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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 315 · 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. 1.61 + 19 =
  2. 2.48 + 19 =
  3. 3.555 − 99 =
  4. 4.31 + 29 =
  5. 5.31 + 19 =
  6. 6.580 + 99 =
  7. 7.66 + 9 =
  8. 8.90 − 29 =
  9. 9.87 − 19 =
  10. 10.70 + 19 =
  11. 11.63 + 9 =
  12. 12.44 + 9 =
  13. 13.23 + 29 =
  14. 14.643 + 99 =
  15. 15.33 + 29 =
  16. 16.629 + 99 =
  17. 17.865 − 99 =
  18. 18.450 − 99 =
  19. 19.77 − 29 =
  20. 20.34 − 9 =
  21. 21.393 + 99 =
  22. 22.68 − 9 =
  23. 23.254 − 99 =
  24. 24.549 − 99 =
  25. 25.70 − 19 =
  26. 26.26 + 29 =
  27. 27.50 + 9 =
  28. 28.42 + 19 =
  29. 29.57 + 19 =
  30. 30.26 − 19 =
  31. 31.75 − 19 =
  32. 32.62 − 19 =
  33. 33.16 − 9 =
  34. 34.72 − 29 =
  35. 35.61 − 19 =
  36. 36.98 − 29 =
  37. 37.63 − 29 =
  38. 38.12 + 29 =
  39. 39.18 + 19 =
  40. 40.66 − 9 =

Answer key

  1. 80
  2. 67
  3. 456
  4. 60
  5. 50
  6. 679
  7. 75
  8. 61
  9. 68
  10. 89
  11. 72
  12. 53
  13. 52
  14. 742
  15. 62
  16. 728
  17. 766
  18. 351
  19. 48
  20. 25
  21. 492
  22. 59
  23. 155
  24. 450
  25. 51
  26. 55
  27. 59
  28. 61
  29. 76
  30. 7
  31. 56
  32. 43
  33. 7
  34. 43
  35. 42
  36. 69
  37. 34
  38. 41
  39. 37
  40. 57

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