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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 699 · 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. 1.73 + 9 =
  2. 2.45 + 9 =
  3. 3.31 + 19 =
  4. 4.596 + 99 =
  5. 5.18 + 9 =
  6. 6.91 − 29 =
  7. 7.17 + 19 =
  8. 8.124 + 99 =
  9. 9.455 + 99 =
  10. 10.58 + 19 =
  11. 11.14 + 9 =
  12. 12.37 − 9 =
  13. 13.44 + 9 =
  14. 14.61 + 29 =
  15. 15.31 − 19 =
  16. 16.52 + 29 =
  17. 17.21 + 19 =
  18. 18.45 − 29 =
  19. 19.49 − 29 =
  20. 20.41 + 19 =
  21. 21.496 + 99 =
  22. 22.433 + 99 =
  23. 23.45 + 19 =
  24. 24.333 + 99 =
  25. 25.79 + 9 =
  26. 26.31 + 29 =
  27. 27.35 + 19 =
  28. 28.79 + 19 =
  29. 29.41 + 9 =
  30. 30.21 + 29 =
  31. 31.14 + 19 =
  32. 32.100 − 29 =
  33. 33.82 − 19 =
  34. 34.69 − 29 =
  35. 35.65 − 9 =
  36. 36.25 + 29 =
  37. 37.36 − 29 =
  38. 38.76 − 19 =
  39. 39.50 − 29 =
  40. 40.87 − 19 =

Answer key

  1. 82
  2. 54
  3. 50
  4. 695
  5. 27
  6. 62
  7. 36
  8. 223
  9. 554
  10. 77
  11. 23
  12. 28
  13. 53
  14. 90
  15. 12
  16. 81
  17. 40
  18. 16
  19. 20
  20. 60
  21. 595
  22. 532
  23. 64
  24. 432
  25. 88
  26. 60
  27. 54
  28. 98
  29. 50
  30. 50
  31. 33
  32. 71
  33. 63
  34. 40
  35. 56
  36. 54
  37. 7
  38. 57
  39. 21
  40. 68

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