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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 77 · 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. 1.23 − 9 =
  2. 2.25 + 29 =
  3. 3.40 + 19 =
  4. 4.54 + 29 =
  5. 5.66 − 29 =
  6. 6.354 − 99 =
  7. 7.77 + 19 =
  8. 8.60 + 29 =
  9. 9.53 + 29 =
  10. 10.61 + 9 =
  11. 11.65 + 19 =
  12. 12.81 − 19 =
  13. 13.26 − 9 =
  14. 14.78 + 9 =
  15. 15.42 + 19 =
  16. 16.633 − 99 =
  17. 17.668 − 99 =
  18. 18.58 + 29 =
  19. 19.541 − 99 =
  20. 20.33 + 29 =
  21. 21.23 + 19 =
  22. 22.31 + 19 =
  23. 23.88 − 29 =
  24. 24.21 + 19 =
  25. 25.45 − 19 =
  26. 26.449 + 99 =
  27. 27.50 − 19 =
  28. 28.102 − 29 =
  29. 29.79 + 29 =
  30. 30.365 + 99 =
  31. 31.28 + 9 =
  32. 32.22 + 29 =
  33. 33.202 + 99 =
  34. 34.77 − 9 =
  35. 35.50 − 9 =
  36. 36.63 + 9 =
  37. 37.355 − 99 =
  38. 38.14 + 29 =
  39. 39.26 + 29 =
  40. 40.28 − 19 =

Answer key

  1. 14
  2. 54
  3. 59
  4. 83
  5. 37
  6. 255
  7. 96
  8. 89
  9. 82
  10. 70
  11. 84
  12. 62
  13. 17
  14. 87
  15. 61
  16. 534
  17. 569
  18. 87
  19. 442
  20. 62
  21. 42
  22. 50
  23. 59
  24. 40
  25. 26
  26. 548
  27. 31
  28. 73
  29. 108
  30. 464
  31. 37
  32. 51
  33. 301
  34. 68
  35. 41
  36. 72
  37. 256
  38. 43
  39. 55
  40. 9

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