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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 378 · 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. 1.43 − 9 =
  2. 2.52 + 19 =
  3. 3.725 − 99 =
  4. 4.92 − 29 =
  5. 5.23 + 9 =
  6. 6.327 + 99 =
  7. 7.247 + 99 =
  8. 8.52 + 29 =
  9. 9.22 + 29 =
  10. 10.79 + 19 =
  11. 11.44 + 9 =
  12. 12.632 + 99 =
  13. 13.12 + 29 =
  14. 14.51 + 29 =
  15. 15.80 − 9 =
  16. 16.63 − 29 =
  17. 17.37 − 19 =
  18. 18.533 − 99 =
  19. 19.39 − 9 =
  20. 20.30 + 9 =
  21. 21.75 − 9 =
  22. 22.40 − 9 =
  23. 23.72 − 29 =
  24. 24.25 + 19 =
  25. 25.745 + 99 =
  26. 26.96 − 19 =
  27. 27.70 + 19 =
  28. 28.69 + 9 =
  29. 29.79 + 9 =
  30. 30.37 + 19 =
  31. 31.26 − 19 =
  32. 32.93 − 29 =
  33. 33.715 + 99 =
  34. 34.199 − 99 =
  35. 35.892 − 99 =
  36. 36.74 − 19 =
  37. 37.78 + 9 =
  38. 38.55 + 19 =
  39. 39.337 + 99 =
  40. 40.439 + 99 =

Answer key

  1. 34
  2. 71
  3. 626
  4. 63
  5. 32
  6. 426
  7. 346
  8. 81
  9. 51
  10. 98
  11. 53
  12. 731
  13. 41
  14. 80
  15. 71
  16. 34
  17. 18
  18. 434
  19. 30
  20. 39
  21. 66
  22. 31
  23. 43
  24. 44
  25. 844
  26. 77
  27. 89
  28. 78
  29. 88
  30. 56
  31. 7
  32. 64
  33. 814
  34. 100
  35. 793
  36. 55
  37. 87
  38. 74
  39. 436
  40. 538

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