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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 686 · 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. 1.50 + 19 =
  2. 2.66 − 19 =
  3. 3.84 − 9 =
  4. 4.44 + 29 =
  5. 5.43 − 19 =
  6. 6.93 − 29 =
  7. 7.32 + 29 =
  8. 8.591 + 99 =
  9. 9.48 + 19 =
  10. 10.459 + 99 =
  11. 11.726 + 99 =
  12. 12.767 − 99 =
  13. 13.37 − 19 =
  14. 14.47 + 9 =
  15. 15.54 + 29 =
  16. 16.52 − 29 =
  17. 17.96 − 19 =
  18. 18.327 + 99 =
  19. 19.224 − 99 =
  20. 20.72 + 29 =
  21. 21.440 + 99 =
  22. 22.553 − 99 =
  23. 23.97 − 29 =
  24. 24.41 − 9 =
  25. 25.66 + 9 =
  26. 26.42 + 9 =
  27. 27.25 + 9 =
  28. 28.92 − 29 =
  29. 29.31 + 9 =
  30. 30.73 − 29 =
  31. 31.76 + 19 =
  32. 32.420 + 99 =
  33. 33.23 − 9 =
  34. 34.76 − 9 =
  35. 35.50 − 29 =
  36. 36.35 + 9 =
  37. 37.20 + 9 =
  38. 38.212 − 99 =
  39. 39.51 + 19 =
  40. 40.42 − 29 =

Answer key

  1. 69
  2. 47
  3. 75
  4. 73
  5. 24
  6. 64
  7. 61
  8. 690
  9. 67
  10. 558
  11. 825
  12. 668
  13. 18
  14. 56
  15. 83
  16. 23
  17. 77
  18. 426
  19. 125
  20. 101
  21. 539
  22. 454
  23. 68
  24. 32
  25. 75
  26. 51
  27. 34
  28. 63
  29. 40
  30. 44
  31. 95
  32. 519
  33. 14
  34. 67
  35. 21
  36. 44
  37. 29
  38. 113
  39. 70
  40. 13

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