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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 748 · 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. 1.69 + 29 =
  2. 2.166 − 99 =
  3. 3.42 + 29 =
  4. 4.81 − 9 =
  5. 5.12 + 29 =
  6. 6.45 + 9 =
  7. 7.36 + 9 =
  8. 8.63 + 19 =
  9. 9.34 + 29 =
  10. 10.21 + 9 =
  11. 11.60 + 9 =
  12. 12.77 − 29 =
  13. 13.284 − 99 =
  14. 14.76 − 9 =
  15. 15.51 − 19 =
  16. 16.561 + 99 =
  17. 17.80 + 19 =
  18. 18.614 + 99 =
  19. 19.40 + 9 =
  20. 20.30 + 9 =
  21. 21.30 + 29 =
  22. 22.15 + 9 =
  23. 23.765 + 99 =
  24. 24.77 − 9 =
  25. 25.25 + 9 =
  26. 26.30 − 19 =
  27. 27.65 − 29 =
  28. 28.84 − 9 =
  29. 29.41 + 9 =
  30. 30.546 − 99 =
  31. 31.80 − 19 =
  32. 32.53 + 9 =
  33. 33.156 + 99 =
  34. 34.710 − 99 =
  35. 35.675 + 99 =
  36. 36.37 + 19 =
  37. 37.61 − 9 =
  38. 38.28 + 19 =
  39. 39.48 + 19 =
  40. 40.287 + 99 =

Answer key

  1. 98
  2. 67
  3. 71
  4. 72
  5. 41
  6. 54
  7. 45
  8. 82
  9. 63
  10. 30
  11. 69
  12. 48
  13. 185
  14. 67
  15. 32
  16. 660
  17. 99
  18. 713
  19. 49
  20. 39
  21. 59
  22. 24
  23. 864
  24. 68
  25. 34
  26. 11
  27. 36
  28. 75
  29. 50
  30. 447
  31. 61
  32. 62
  33. 255
  34. 611
  35. 774
  36. 56
  37. 52
  38. 47
  39. 67
  40. 386

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