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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 984 · 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. 1.514 + 99 =
  2. 2.55 − 9 =
  3. 3.641 − 99 =
  4. 4.48 + 9 =
  5. 5.25 − 9 =
  6. 6.768 − 99 =
  7. 7.33 − 29 =
  8. 8.26 − 9 =
  9. 9.302 − 99 =
  10. 10.76 − 19 =
  11. 11.461 + 99 =
  12. 12.46 − 19 =
  13. 13.866 − 99 =
  14. 14.242 − 99 =
  15. 15.51 − 19 =
  16. 16.17 − 9 =
  17. 17.78 + 29 =
  18. 18.645 − 99 =
  19. 19.431 − 99 =
  20. 20.19 − 9 =
  21. 21.75 + 19 =
  22. 22.402 − 99 =
  23. 23.93 − 19 =
  24. 24.47 + 19 =
  25. 25.17 + 9 =
  26. 26.30 + 29 =
  27. 27.758 + 99 =
  28. 28.18 + 19 =
  29. 29.53 + 9 =
  30. 30.22 − 19 =
  31. 31.52 + 19 =
  32. 32.513 + 99 =
  33. 33.778 − 99 =
  34. 34.18 + 29 =
  35. 35.99 − 19 =
  36. 36.25 + 19 =
  37. 37.29 + 9 =
  38. 38.15 − 9 =
  39. 39.199 + 99 =
  40. 40.13 + 19 =

Answer key

  1. 613
  2. 46
  3. 542
  4. 57
  5. 16
  6. 669
  7. 4
  8. 17
  9. 203
  10. 57
  11. 560
  12. 27
  13. 767
  14. 143
  15. 32
  16. 8
  17. 107
  18. 546
  19. 332
  20. 10
  21. 94
  22. 303
  23. 74
  24. 66
  25. 26
  26. 59
  27. 857
  28. 37
  29. 62
  30. 3
  31. 71
  32. 612
  33. 679
  34. 47
  35. 80
  36. 44
  37. 38
  38. 6
  39. 298
  40. 32

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