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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 778 · 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. 1.62 − 19 =
  2. 2.72 + 9 =
  3. 3.219 + 99 =
  4. 4.75 + 9 =
  5. 5.39 + 19 =
  6. 6.181 + 99 =
  7. 7.228 − 99 =
  8. 8.15 + 29 =
  9. 9.38 + 9 =
  10. 10.655 − 99 =
  11. 11.33 + 29 =
  12. 12.41 − 29 =
  13. 13.162 − 99 =
  14. 14.53 + 19 =
  15. 15.168 + 99 =
  16. 16.92 − 29 =
  17. 17.879 − 99 =
  18. 18.70 + 9 =
  19. 19.25 − 9 =
  20. 20.79 − 29 =
  21. 21.16 + 19 =
  22. 22.734 + 99 =
  23. 23.58 + 29 =
  24. 24.415 + 99 =
  25. 25.50 + 9 =
  26. 26.22 + 19 =
  27. 27.13 + 19 =
  28. 28.49 − 9 =
  29. 29.110 + 99 =
  30. 30.26 − 9 =
  31. 31.18 + 9 =
  32. 32.88 − 19 =
  33. 33.67 − 29 =
  34. 34.80 + 29 =
  35. 35.191 + 99 =
  36. 36.669 − 99 =
  37. 37.109 − 29 =
  38. 38.65 − 9 =
  39. 39.13 − 9 =
  40. 40.66 − 29 =

Answer key

  1. 43
  2. 81
  3. 318
  4. 84
  5. 58
  6. 280
  7. 129
  8. 44
  9. 47
  10. 556
  11. 62
  12. 12
  13. 63
  14. 72
  15. 267
  16. 63
  17. 780
  18. 79
  19. 16
  20. 50
  21. 35
  22. 833
  23. 87
  24. 514
  25. 59
  26. 41
  27. 32
  28. 40
  29. 209
  30. 17
  31. 27
  32. 69
  33. 38
  34. 109
  35. 290
  36. 570
  37. 80
  38. 56
  39. 4
  40. 37

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