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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 757 · 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. 1.63 − 29 =
  2. 2.460 + 99 =
  3. 3.127 + 99 =
  4. 4.25 + 9 =
  5. 5.79 − 29 =
  6. 6.97 − 19 =
  7. 7.203 + 99 =
  8. 8.79 − 9 =
  9. 9.340 − 99 =
  10. 10.521 + 99 =
  11. 11.33 + 19 =
  12. 12.49 + 19 =
  13. 13.272 + 99 =
  14. 14.377 + 99 =
  15. 15.76 − 19 =
  16. 16.62 + 9 =
  17. 17.21 − 9 =
  18. 18.27 − 9 =
  19. 19.14 + 19 =
  20. 20.106 + 99 =
  21. 21.25 + 19 =
  22. 22.39 − 19 =
  23. 23.52 − 19 =
  24. 24.55 − 19 =
  25. 25.47 + 19 =
  26. 26.96 − 29 =
  27. 27.19 + 9 =
  28. 28.77 + 19 =
  29. 29.850 − 99 =
  30. 30.622 + 99 =
  31. 31.446 − 99 =
  32. 32.453 + 99 =
  33. 33.31 − 9 =
  34. 34.60 − 9 =
  35. 35.179 − 99 =
  36. 36.514 + 99 =
  37. 37.64 − 29 =
  38. 38.676 − 99 =
  39. 39.72 + 19 =
  40. 40.519 + 99 =

Answer key

  1. 34
  2. 559
  3. 226
  4. 34
  5. 50
  6. 78
  7. 302
  8. 70
  9. 241
  10. 620
  11. 52
  12. 68
  13. 371
  14. 476
  15. 57
  16. 71
  17. 12
  18. 18
  19. 33
  20. 205
  21. 44
  22. 20
  23. 33
  24. 36
  25. 66
  26. 67
  27. 28
  28. 96
  29. 751
  30. 721
  31. 347
  32. 552
  33. 22
  34. 51
  35. 80
  36. 613
  37. 35
  38. 577
  39. 91
  40. 618

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