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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 924 · 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. 1.651 − 99 =
  2. 2.515 + 99 =
  3. 3.87 − 9 =
  4. 4.363 + 99 =
  5. 5.47 − 29 =
  6. 6.79 − 29 =
  7. 7.605 − 99 =
  8. 8.17 + 9 =
  9. 9.53 − 9 =
  10. 10.34 + 19 =
  11. 11.613 − 99 =
  12. 12.42 + 29 =
  13. 13.48 + 19 =
  14. 14.67 − 19 =
  15. 15.47 + 19 =
  16. 16.593 + 99 =
  17. 17.83 − 9 =
  18. 18.64 + 29 =
  19. 19.759 − 99 =
  20. 20.20 + 9 =
  21. 21.27 + 19 =
  22. 22.193 − 99 =
  23. 23.45 − 19 =
  24. 24.603 − 99 =
  25. 25.63 − 19 =
  26. 26.38 + 9 =
  27. 27.678 + 99 =
  28. 28.37 + 19 =
  29. 29.206 − 99 =
  30. 30.270 − 99 =
  31. 31.517 − 99 =
  32. 32.94 − 19 =
  33. 33.51 − 19 =
  34. 34.14 + 29 =
  35. 35.318 − 99 =
  36. 36.745 + 99 =
  37. 37.62 + 19 =
  38. 38.66 − 29 =
  39. 39.82 − 19 =
  40. 40.373 + 99 =

Answer key

  1. 552
  2. 614
  3. 78
  4. 462
  5. 18
  6. 50
  7. 506
  8. 26
  9. 44
  10. 53
  11. 514
  12. 71
  13. 67
  14. 48
  15. 66
  16. 692
  17. 74
  18. 93
  19. 660
  20. 29
  21. 46
  22. 94
  23. 26
  24. 504
  25. 44
  26. 47
  27. 777
  28. 56
  29. 107
  30. 171
  31. 418
  32. 75
  33. 32
  34. 43
  35. 219
  36. 844
  37. 81
  38. 37
  39. 63
  40. 472

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