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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 375 · 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. 1.13 − 9 =
  2. 2.219 − 99 =
  3. 3.77 − 29 =
  4. 4.30 − 9 =
  5. 5.32 − 19 =
  6. 6.12 + 19 =
  7. 7.34 + 9 =
  8. 8.87 − 19 =
  9. 9.20 + 9 =
  10. 10.46 + 19 =
  11. 11.34 − 29 =
  12. 12.34 + 29 =
  13. 13.80 − 9 =
  14. 14.74 − 9 =
  15. 15.497 − 99 =
  16. 16.47 + 9 =
  17. 17.71 + 9 =
  18. 18.46 + 29 =
  19. 19.29 + 9 =
  20. 20.15 + 9 =
  21. 21.597 − 99 =
  22. 22.18 + 19 =
  23. 23.29 + 29 =
  24. 24.24 + 9 =
  25. 25.33 + 29 =
  26. 26.19 + 29 =
  27. 27.580 − 99 =
  28. 28.59 − 9 =
  29. 29.44 + 9 =
  30. 30.27 + 9 =
  31. 31.67 − 29 =
  32. 32.56 − 19 =
  33. 33.193 + 99 =
  34. 34.27 + 19 =
  35. 35.72 + 9 =
  36. 36.57 + 9 =
  37. 37.177 + 99 =
  38. 38.43 − 19 =
  39. 39.80 + 9 =
  40. 40.27 − 19 =

Answer key

  1. 4
  2. 120
  3. 48
  4. 21
  5. 13
  6. 31
  7. 43
  8. 68
  9. 29
  10. 65
  11. 5
  12. 63
  13. 71
  14. 65
  15. 398
  16. 56
  17. 80
  18. 75
  19. 38
  20. 24
  21. 498
  22. 37
  23. 58
  24. 33
  25. 62
  26. 48
  27. 481
  28. 50
  29. 53
  30. 36
  31. 38
  32. 37
  33. 292
  34. 46
  35. 81
  36. 66
  37. 276
  38. 24
  39. 89
  40. 8

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