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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 190 · 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. 1.704 + 99 =
  2. 2.59 + 19 =
  3. 3.35 + 29 =
  4. 4.62 + 9 =
  5. 5.619 − 99 =
  6. 6.31 + 9 =
  7. 7.69 − 29 =
  8. 8.174 − 99 =
  9. 9.27 − 19 =
  10. 10.97 − 19 =
  11. 11.299 − 99 =
  12. 12.99 − 29 =
  13. 13.51 + 9 =
  14. 14.570 + 99 =
  15. 15.655 + 99 =
  16. 16.61 + 9 =
  17. 17.38 + 9 =
  18. 18.66 − 9 =
  19. 19.55 + 29 =
  20. 20.45 − 29 =
  21. 21.109 + 99 =
  22. 22.13 − 9 =
  23. 23.504 + 99 =
  24. 24.30 + 29 =
  25. 25.351 + 99 =
  26. 26.26 − 19 =
  27. 27.68 − 9 =
  28. 28.740 + 99 =
  29. 29.90 − 29 =
  30. 30.70 − 19 =
  31. 31.76 − 29 =
  32. 32.41 + 9 =
  33. 33.47 − 19 =
  34. 34.500 − 99 =
  35. 35.58 + 9 =
  36. 36.26 − 9 =
  37. 37.52 − 29 =
  38. 38.75 + 9 =
  39. 39.48 − 19 =
  40. 40.79 + 19 =

Answer key

  1. 803
  2. 78
  3. 64
  4. 71
  5. 520
  6. 40
  7. 40
  8. 75
  9. 8
  10. 78
  11. 200
  12. 70
  13. 60
  14. 669
  15. 754
  16. 70
  17. 47
  18. 57
  19. 84
  20. 16
  21. 208
  22. 4
  23. 603
  24. 59
  25. 450
  26. 7
  27. 59
  28. 839
  29. 61
  30. 51
  31. 47
  32. 50
  33. 28
  34. 401
  35. 67
  36. 17
  37. 23
  38. 84
  39. 29
  40. 98

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