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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 269 · 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. 1.66 + 19 =
  2. 2.33 + 9 =
  3. 3.141 + 99 =
  4. 4.48 − 19 =
  5. 5.26 − 9 =
  6. 6.49 + 19 =
  7. 7.64 − 29 =
  8. 8.25 − 19 =
  9. 9.33 − 29 =
  10. 10.28 + 9 =
  11. 11.26 + 9 =
  12. 12.55 − 29 =
  13. 13.24 + 9 =
  14. 14.26 + 29 =
  15. 15.305 − 99 =
  16. 16.479 + 99 =
  17. 17.158 + 99 =
  18. 18.25 + 19 =
  19. 19.70 − 29 =
  20. 20.31 − 9 =
  21. 21.64 − 19 =
  22. 22.446 + 99 =
  23. 23.379 − 99 =
  24. 24.39 + 9 =
  25. 25.571 − 99 =
  26. 26.211 + 99 =
  27. 27.78 − 29 =
  28. 28.21 + 9 =
  29. 29.19 − 9 =
  30. 30.110 + 99 =
  31. 31.703 + 99 =
  32. 32.88 − 29 =
  33. 33.713 − 99 =
  34. 34.68 + 9 =
  35. 35.74 + 9 =
  36. 36.31 + 9 =
  37. 37.38 + 29 =
  38. 38.93 − 29 =
  39. 39.13 + 29 =
  40. 40.85 − 29 =

Answer key

  1. 85
  2. 42
  3. 240
  4. 29
  5. 17
  6. 68
  7. 35
  8. 6
  9. 4
  10. 37
  11. 35
  12. 26
  13. 33
  14. 55
  15. 206
  16. 578
  17. 257
  18. 44
  19. 41
  20. 22
  21. 45
  22. 545
  23. 280
  24. 48
  25. 472
  26. 310
  27. 49
  28. 30
  29. 10
  30. 209
  31. 802
  32. 59
  33. 614
  34. 77
  35. 83
  36. 40
  37. 67
  38. 64
  39. 42
  40. 56

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