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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 505 · 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. 1.45 + 9 =
  2. 2.533 + 99 =
  3. 3.17 + 29 =
  4. 4.30 − 9 =
  5. 5.65 + 9 =
  6. 6.24 + 9 =
  7. 7.26 + 9 =
  8. 8.21 − 9 =
  9. 9.50 − 19 =
  10. 10.71 + 29 =
  11. 11.19 − 9 =
  12. 12.18 − 9 =
  13. 13.14 + 9 =
  14. 14.56 + 29 =
  15. 15.250 + 99 =
  16. 16.54 + 9 =
  17. 17.64 + 19 =
  18. 18.48 − 29 =
  19. 19.137 + 99 =
  20. 20.35 + 9 =
  21. 21.43 − 19 =
  22. 22.23 + 9 =
  23. 23.55 + 29 =
  24. 24.59 − 9 =
  25. 25.66 + 9 =
  26. 26.23 − 9 =
  27. 27.33 − 19 =
  28. 28.213 + 99 =
  29. 29.14 + 29 =
  30. 30.689 + 99 =
  31. 31.61 + 9 =
  32. 32.47 − 9 =
  33. 33.21 + 19 =
  34. 34.509 + 99 =
  35. 35.56 + 19 =
  36. 36.44 + 9 =
  37. 37.41 + 19 =
  38. 38.63 − 29 =
  39. 39.277 + 99 =
  40. 40.771 + 99 =

Answer key

  1. 54
  2. 632
  3. 46
  4. 21
  5. 74
  6. 33
  7. 35
  8. 12
  9. 31
  10. 100
  11. 10
  12. 9
  13. 23
  14. 85
  15. 349
  16. 63
  17. 83
  18. 19
  19. 236
  20. 44
  21. 24
  22. 32
  23. 84
  24. 50
  25. 75
  26. 14
  27. 14
  28. 312
  29. 43
  30. 788
  31. 70
  32. 38
  33. 40
  34. 608
  35. 75
  36. 53
  37. 60
  38. 34
  39. 376
  40. 870

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