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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 329 · 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. 1.20 + 9 =
  2. 2.26 − 9 =
  3. 3.115 + 99 =
  4. 4.56 + 9 =
  5. 5.691 + 99 =
  6. 6.92 − 19 =
  7. 7.35 − 9 =
  8. 8.51 − 9 =
  9. 9.22 − 9 =
  10. 10.15 + 19 =
  11. 11.64 + 9 =
  12. 12.23 − 9 =
  13. 13.785 − 99 =
  14. 14.255 − 99 =
  15. 15.33 − 29 =
  16. 16.84 − 9 =
  17. 17.47 + 19 =
  18. 18.29 + 29 =
  19. 19.43 + 29 =
  20. 20.29 + 19 =
  21. 21.552 − 99 =
  22. 22.35 − 29 =
  23. 23.380 + 99 =
  24. 24.635 + 99 =
  25. 25.19 + 19 =
  26. 26.36 + 19 =
  27. 27.75 + 9 =
  28. 28.59 − 9 =
  29. 29.53 − 19 =
  30. 30.56 − 9 =
  31. 31.45 + 19 =
  32. 32.34 + 29 =
  33. 33.88 − 29 =
  34. 34.284 − 99 =
  35. 35.562 + 99 =
  36. 36.63 − 9 =
  37. 37.53 + 9 =
  38. 38.72 + 9 =
  39. 39.30 + 29 =
  40. 40.630 − 99 =

Answer key

  1. 29
  2. 17
  3. 214
  4. 65
  5. 790
  6. 73
  7. 26
  8. 42
  9. 13
  10. 34
  11. 73
  12. 14
  13. 686
  14. 156
  15. 4
  16. 75
  17. 66
  18. 58
  19. 72
  20. 48
  21. 453
  22. 6
  23. 479
  24. 734
  25. 38
  26. 55
  27. 84
  28. 50
  29. 34
  30. 47
  31. 64
  32. 63
  33. 59
  34. 185
  35. 661
  36. 54
  37. 62
  38. 81
  39. 59
  40. 531

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