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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 319 · 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. 1.343 + 99 =
  2. 2.757 + 99 =
  3. 3.52 − 29 =
  4. 4.56 + 9 =
  5. 5.730 + 99 =
  6. 6.39 + 19 =
  7. 7.38 − 19 =
  8. 8.76 − 9 =
  9. 9.425 + 99 =
  10. 10.70 + 29 =
  11. 11.117 + 99 =
  12. 12.31 + 9 =
  13. 13.734 + 99 =
  14. 14.162 − 99 =
  15. 15.792 − 99 =
  16. 16.33 − 29 =
  17. 17.24 − 9 =
  18. 18.21 + 9 =
  19. 19.570 + 99 =
  20. 20.47 − 29 =
  21. 21.50 + 9 =
  22. 22.79 + 9 =
  23. 23.262 − 99 =
  24. 24.74 − 9 =
  25. 25.44 − 19 =
  26. 26.430 − 99 =
  27. 27.715 + 99 =
  28. 28.225 + 99 =
  29. 29.685 + 99 =
  30. 30.29 − 9 =
  31. 31.73 + 9 =
  32. 32.94 − 19 =
  33. 33.32 − 9 =
  34. 34.27 + 19 =
  35. 35.62 + 9 =
  36. 36.588 − 99 =
  37. 37.65 + 9 =
  38. 38.13 + 9 =
  39. 39.39 + 9 =
  40. 40.26 − 9 =

Answer key

  1. 442
  2. 856
  3. 23
  4. 65
  5. 829
  6. 58
  7. 19
  8. 67
  9. 524
  10. 99
  11. 216
  12. 40
  13. 833
  14. 63
  15. 693
  16. 4
  17. 15
  18. 30
  19. 669
  20. 18
  21. 59
  22. 88
  23. 163
  24. 65
  25. 25
  26. 331
  27. 814
  28. 324
  29. 784
  30. 20
  31. 82
  32. 75
  33. 23
  34. 46
  35. 71
  36. 489
  37. 74
  38. 22
  39. 48
  40. 17

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