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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 738 · 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. 1.72 + 19 =
  2. 2.47 − 19 =
  3. 3.24 − 19 =
  4. 4.50 + 29 =
  5. 5.76 + 9 =
  6. 6.43 + 29 =
  7. 7.61 + 19 =
  8. 8.619 + 99 =
  9. 9.161 − 99 =
  10. 10.69 + 9 =
  11. 11.63 − 9 =
  12. 12.29 + 29 =
  13. 13.15 + 19 =
  14. 14.392 − 99 =
  15. 15.15 − 9 =
  16. 16.428 − 99 =
  17. 17.638 − 99 =
  18. 18.639 + 99 =
  19. 19.73 + 29 =
  20. 20.340 + 99 =
  21. 21.30 + 9 =
  22. 22.28 + 9 =
  23. 23.18 + 29 =
  24. 24.65 + 29 =
  25. 25.44 + 9 =
  26. 26.28 + 19 =
  27. 27.42 + 9 =
  28. 28.83 − 29 =
  29. 29.523 − 99 =
  30. 30.743 + 99 =
  31. 31.662 − 99 =
  32. 32.38 − 19 =
  33. 33.14 + 9 =
  34. 34.792 + 99 =
  35. 35.86 − 19 =
  36. 36.69 + 29 =
  37. 37.29 − 9 =
  38. 38.794 + 99 =
  39. 39.27 + 19 =
  40. 40.326 + 99 =

Answer key

  1. 91
  2. 28
  3. 5
  4. 79
  5. 85
  6. 72
  7. 80
  8. 718
  9. 62
  10. 78
  11. 54
  12. 58
  13. 34
  14. 293
  15. 6
  16. 329
  17. 539
  18. 738
  19. 102
  20. 439
  21. 39
  22. 37
  23. 47
  24. 94
  25. 53
  26. 47
  27. 51
  28. 54
  29. 424
  30. 842
  31. 563
  32. 19
  33. 23
  34. 891
  35. 67
  36. 98
  37. 20
  38. 893
  39. 46
  40. 425

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