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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 357 · 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. 1.223 − 99 =
  2. 2.79 + 19 =
  3. 3.20 − 9 =
  4. 4.33 − 9 =
  5. 5.46 + 9 =
  6. 6.327 + 99 =
  7. 7.51 + 9 =
  8. 8.101 − 29 =
  9. 9.546 + 99 =
  10. 10.71 + 9 =
  11. 11.803 − 99 =
  12. 12.78 − 19 =
  13. 13.534 + 99 =
  14. 14.22 + 9 =
  15. 15.34 − 19 =
  16. 16.570 + 99 =
  17. 17.68 − 9 =
  18. 18.74 + 9 =
  19. 19.54 + 29 =
  20. 20.147 + 99 =
  21. 21.20 + 29 =
  22. 22.41 − 19 =
  23. 23.47 − 9 =
  24. 24.31 − 9 =
  25. 25.232 + 99 =
  26. 26.18 − 9 =
  27. 27.51 − 29 =
  28. 28.72 + 19 =
  29. 29.14 + 29 =
  30. 30.14 − 9 =
  31. 31.60 − 29 =
  32. 32.442 − 99 =
  33. 33.85 − 9 =
  34. 34.428 + 99 =
  35. 35.18 + 19 =
  36. 36.75 + 9 =
  37. 37.42 + 19 =
  38. 38.15 + 19 =
  39. 39.61 + 19 =
  40. 40.458 + 99 =

Answer key

  1. 124
  2. 98
  3. 11
  4. 24
  5. 55
  6. 426
  7. 60
  8. 72
  9. 645
  10. 80
  11. 704
  12. 59
  13. 633
  14. 31
  15. 15
  16. 669
  17. 59
  18. 83
  19. 83
  20. 246
  21. 49
  22. 22
  23. 38
  24. 22
  25. 331
  26. 9
  27. 22
  28. 91
  29. 43
  30. 5
  31. 31
  32. 343
  33. 76
  34. 527
  35. 37
  36. 84
  37. 61
  38. 34
  39. 80
  40. 557

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