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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 733 · 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. 1.14 + 29 =
  2. 2.62 + 19 =
  3. 3.28 + 29 =
  4. 4.395 − 99 =
  5. 5.22 − 9 =
  6. 6.42 − 19 =
  7. 7.78 + 29 =
  8. 8.61 + 9 =
  9. 9.588 − 99 =
  10. 10.81 − 29 =
  11. 11.37 + 19 =
  12. 12.105 − 29 =
  13. 13.15 + 9 =
  14. 14.52 + 19 =
  15. 15.75 − 9 =
  16. 16.214 − 99 =
  17. 17.14 + 19 =
  18. 18.79 − 19 =
  19. 19.37 + 9 =
  20. 20.66 + 19 =
  21. 21.130 + 99 =
  22. 22.68 − 19 =
  23. 23.43 + 9 =
  24. 24.110 + 99 =
  25. 25.71 − 29 =
  26. 26.53 − 29 =
  27. 27.389 − 99 =
  28. 28.105 + 99 =
  29. 29.14 + 9 =
  30. 30.63 + 29 =
  31. 31.301 + 99 =
  32. 32.45 + 29 =
  33. 33.74 + 29 =
  34. 34.80 + 19 =
  35. 35.34 − 19 =
  36. 36.536 − 99 =
  37. 37.676 + 99 =
  38. 38.55 − 29 =
  39. 39.369 − 99 =
  40. 40.41 − 29 =

Answer key

  1. 43
  2. 81
  3. 57
  4. 296
  5. 13
  6. 23
  7. 107
  8. 70
  9. 489
  10. 52
  11. 56
  12. 76
  13. 24
  14. 71
  15. 66
  16. 115
  17. 33
  18. 60
  19. 46
  20. 85
  21. 229
  22. 49
  23. 52
  24. 209
  25. 42
  26. 24
  27. 290
  28. 204
  29. 23
  30. 92
  31. 400
  32. 74
  33. 103
  34. 99
  35. 15
  36. 437
  37. 775
  38. 26
  39. 270
  40. 12

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