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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 861 · 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. 1.459 + 99 =
  2. 2.16 + 29 =
  3. 3.291 + 99 =
  4. 4.57 − 9 =
  5. 5.26 + 9 =
  6. 6.47 − 29 =
  7. 7.35 − 19 =
  8. 8.32 − 9 =
  9. 9.35 − 9 =
  10. 10.55 − 29 =
  11. 11.713 − 99 =
  12. 12.241 − 99 =
  13. 13.44 + 9 =
  14. 14.29 + 19 =
  15. 15.524 + 99 =
  16. 16.31 + 19 =
  17. 17.282 + 99 =
  18. 18.42 − 29 =
  19. 19.65 + 9 =
  20. 20.43 + 9 =
  21. 21.694 + 99 =
  22. 22.85 − 19 =
  23. 23.37 + 9 =
  24. 24.424 − 99 =
  25. 25.68 − 19 =
  26. 26.250 + 99 =
  27. 27.37 − 19 =
  28. 28.80 + 19 =
  29. 29.27 − 19 =
  30. 30.165 + 99 =
  31. 31.711 + 99 =
  32. 32.80 − 9 =
  33. 33.20 + 9 =
  34. 34.99 − 19 =
  35. 35.49 − 29 =
  36. 36.15 + 19 =
  37. 37.58 + 9 =
  38. 38.24 + 9 =
  39. 39.69 − 9 =
  40. 40.315 + 99 =

Answer key

  1. 558
  2. 45
  3. 390
  4. 48
  5. 35
  6. 18
  7. 16
  8. 23
  9. 26
  10. 26
  11. 614
  12. 142
  13. 53
  14. 48
  15. 623
  16. 50
  17. 381
  18. 13
  19. 74
  20. 52
  21. 793
  22. 66
  23. 46
  24. 325
  25. 49
  26. 349
  27. 18
  28. 99
  29. 8
  30. 264
  31. 810
  32. 71
  33. 29
  34. 80
  35. 20
  36. 34
  37. 67
  38. 33
  39. 60
  40. 414

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