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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 799 · 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. 1.28 + 29 =
  2. 2.560 − 99 =
  3. 3.12 + 29 =
  4. 4.37 + 19 =
  5. 5.51 + 9 =
  6. 6.15 + 19 =
  7. 7.634 − 99 =
  8. 8.24 + 9 =
  9. 9.69 + 9 =
  10. 10.357 − 99 =
  11. 11.75 + 19 =
  12. 12.55 − 19 =
  13. 13.13 + 9 =
  14. 14.37 − 29 =
  15. 15.658 − 99 =
  16. 16.33 − 29 =
  17. 17.851 − 99 =
  18. 18.802 − 99 =
  19. 19.572 − 99 =
  20. 20.497 + 99 =
  21. 21.84 − 9 =
  22. 22.392 + 99 =
  23. 23.44 − 9 =
  24. 24.26 + 19 =
  25. 25.72 + 19 =
  26. 26.53 − 9 =
  27. 27.676 − 99 =
  28. 28.849 − 99 =
  29. 29.30 + 19 =
  30. 30.79 − 9 =
  31. 31.26 − 9 =
  32. 32.68 + 9 =
  33. 33.41 − 29 =
  34. 34.44 − 29 =
  35. 35.38 + 19 =
  36. 36.27 − 19 =
  37. 37.70 − 19 =
  38. 38.30 − 9 =
  39. 39.79 + 9 =
  40. 40.65 + 9 =

Answer key

  1. 57
  2. 461
  3. 41
  4. 56
  5. 60
  6. 34
  7. 535
  8. 33
  9. 78
  10. 258
  11. 94
  12. 36
  13. 22
  14. 8
  15. 559
  16. 4
  17. 752
  18. 703
  19. 473
  20. 596
  21. 75
  22. 491
  23. 35
  24. 45
  25. 91
  26. 44
  27. 577
  28. 750
  29. 49
  30. 70
  31. 17
  32. 77
  33. 12
  34. 15
  35. 57
  36. 8
  37. 51
  38. 21
  39. 88
  40. 74

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