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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 382 · 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. 1.614 + 99 =
  2. 2.65 + 19 =
  3. 3.32 + 9 =
  4. 4.42 − 9 =
  5. 5.51 − 9 =
  6. 6.70 + 9 =
  7. 7.144 + 99 =
  8. 8.45 + 19 =
  9. 9.660 + 99 =
  10. 10.358 − 99 =
  11. 11.30 + 19 =
  12. 12.42 + 9 =
  13. 13.31 − 19 =
  14. 14.50 − 29 =
  15. 15.21 + 29 =
  16. 16.784 + 99 =
  17. 17.17 − 9 =
  18. 18.51 − 19 =
  19. 19.40 − 9 =
  20. 20.72 + 19 =
  21. 21.38 − 9 =
  22. 22.191 + 99 =
  23. 23.36 + 19 =
  24. 24.24 + 9 =
  25. 25.361 − 99 =
  26. 26.13 + 9 =
  27. 27.534 + 99 =
  28. 28.51 − 29 =
  29. 29.72 − 9 =
  30. 30.63 − 29 =
  31. 31.50 + 9 =
  32. 32.29 + 29 =
  33. 33.71 + 9 =
  34. 34.670 + 99 =
  35. 35.369 − 99 =
  36. 36.38 − 19 =
  37. 37.55 + 29 =
  38. 38.77 − 29 =
  39. 39.60 + 19 =
  40. 40.53 − 19 =

Answer key

  1. 713
  2. 84
  3. 41
  4. 33
  5. 42
  6. 79
  7. 243
  8. 64
  9. 759
  10. 259
  11. 49
  12. 51
  13. 12
  14. 21
  15. 50
  16. 883
  17. 8
  18. 32
  19. 31
  20. 91
  21. 29
  22. 290
  23. 55
  24. 33
  25. 262
  26. 22
  27. 633
  28. 22
  29. 63
  30. 34
  31. 59
  32. 58
  33. 80
  34. 769
  35. 270
  36. 19
  37. 84
  38. 48
  39. 79
  40. 34

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