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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 803 · 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. 1.26 + 9 =
  2. 2.30 − 19 =
  3. 3.60 + 19 =
  4. 4.60 − 19 =
  5. 5.75 + 19 =
  6. 6.652 − 99 =
  7. 7.107 − 29 =
  8. 8.281 + 99 =
  9. 9.74 + 29 =
  10. 10.30 + 9 =
  11. 11.72 − 29 =
  12. 12.20 + 29 =
  13. 13.798 − 99 =
  14. 14.133 + 99 =
  15. 15.61 − 29 =
  16. 16.196 − 99 =
  17. 17.54 − 29 =
  18. 18.23 + 29 =
  19. 19.66 + 9 =
  20. 20.77 + 9 =
  21. 21.13 + 19 =
  22. 22.108 − 29 =
  23. 23.70 − 19 =
  24. 24.45 − 29 =
  25. 25.79 − 19 =
  26. 26.695 − 99 =
  27. 27.49 − 9 =
  28. 28.69 − 19 =
  29. 29.599 + 99 =
  30. 30.442 + 99 =
  31. 31.27 + 29 =
  32. 32.34 + 29 =
  33. 33.78 + 29 =
  34. 34.36 − 9 =
  35. 35.22 + 29 =
  36. 36.18 − 9 =
  37. 37.367 − 99 =
  38. 38.52 + 29 =
  39. 39.80 − 29 =
  40. 40.24 − 19 =

Answer key

  1. 35
  2. 11
  3. 79
  4. 41
  5. 94
  6. 553
  7. 78
  8. 380
  9. 103
  10. 39
  11. 43
  12. 49
  13. 699
  14. 232
  15. 32
  16. 97
  17. 25
  18. 52
  19. 75
  20. 86
  21. 32
  22. 79
  23. 51
  24. 16
  25. 60
  26. 596
  27. 40
  28. 50
  29. 698
  30. 541
  31. 56
  32. 63
  33. 107
  34. 27
  35. 51
  36. 9
  37. 268
  38. 81
  39. 51
  40. 5

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