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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 754 · 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. 1.19 + 19 =
  2. 2.25 + 9 =
  3. 3.18 − 9 =
  4. 4.62 + 19 =
  5. 5.74 − 9 =
  6. 6.186 − 99 =
  7. 7.230 − 99 =
  8. 8.53 + 19 =
  9. 9.73 + 19 =
  10. 10.16 + 9 =
  11. 11.347 − 99 =
  12. 12.51 − 19 =
  13. 13.13 − 9 =
  14. 14.39 + 19 =
  15. 15.24 + 9 =
  16. 16.73 − 29 =
  17. 17.87 − 9 =
  18. 18.37 − 9 =
  19. 19.60 + 29 =
  20. 20.303 + 99 =
  21. 21.54 + 19 =
  22. 22.91 − 19 =
  23. 23.49 + 19 =
  24. 24.104 − 29 =
  25. 25.498 − 99 =
  26. 26.69 − 19 =
  27. 27.60 + 9 =
  28. 28.90 − 19 =
  29. 29.29 + 19 =
  30. 30.31 + 19 =
  31. 31.39 + 9 =
  32. 32.642 + 99 =
  33. 33.42 + 9 =
  34. 34.44 + 19 =
  35. 35.30 + 19 =
  36. 36.582 − 99 =
  37. 37.76 − 29 =
  38. 38.50 − 29 =
  39. 39.717 − 99 =
  40. 40.48 − 9 =

Answer key

  1. 38
  2. 34
  3. 9
  4. 81
  5. 65
  6. 87
  7. 131
  8. 72
  9. 92
  10. 25
  11. 248
  12. 32
  13. 4
  14. 58
  15. 33
  16. 44
  17. 78
  18. 28
  19. 89
  20. 402
  21. 73
  22. 72
  23. 68
  24. 75
  25. 399
  26. 50
  27. 69
  28. 71
  29. 48
  30. 50
  31. 48
  32. 741
  33. 51
  34. 63
  35. 49
  36. 483
  37. 47
  38. 21
  39. 618
  40. 39

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