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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 647 · 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. 1.15 + 9 =
  2. 2.36 + 9 =
  3. 3.18 − 9 =
  4. 4.17 − 9 =
  5. 5.31 − 19 =
  6. 6.57 − 9 =
  7. 7.41 + 9 =
  8. 8.46 − 9 =
  9. 9.83 − 9 =
  10. 10.334 − 99 =
  11. 11.88 − 9 =
  12. 12.35 + 9 =
  13. 13.20 + 9 =
  14. 14.346 + 99 =
  15. 15.31 + 29 =
  16. 16.155 − 99 =
  17. 17.81 − 9 =
  18. 18.13 + 19 =
  19. 19.24 − 9 =
  20. 20.32 + 9 =
  21. 21.55 + 19 =
  22. 22.13 + 29 =
  23. 23.382 + 99 =
  24. 24.239 − 99 =
  25. 25.70 + 9 =
  26. 26.72 + 29 =
  27. 27.54 − 9 =
  28. 28.35 − 9 =
  29. 29.50 + 29 =
  30. 30.661 + 99 =
  31. 31.75 − 9 =
  32. 32.337 − 99 =
  33. 33.48 + 19 =
  34. 34.15 + 29 =
  35. 35.45 − 9 =
  36. 36.65 + 19 =
  37. 37.56 + 19 =
  38. 38.489 − 99 =
  39. 39.17 + 19 =
  40. 40.34 + 29 =

Answer key

  1. 24
  2. 45
  3. 9
  4. 8
  5. 12
  6. 48
  7. 50
  8. 37
  9. 74
  10. 235
  11. 79
  12. 44
  13. 29
  14. 445
  15. 60
  16. 56
  17. 72
  18. 32
  19. 15
  20. 41
  21. 74
  22. 42
  23. 481
  24. 140
  25. 79
  26. 101
  27. 45
  28. 26
  29. 79
  30. 760
  31. 66
  32. 238
  33. 67
  34. 44
  35. 36
  36. 84
  37. 75
  38. 390
  39. 36
  40. 63

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