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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 522 · 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. 1.65 − 29 =
  2. 2.34 − 29 =
  3. 3.653 − 99 =
  4. 4.39 − 19 =
  5. 5.35 − 29 =
  6. 6.30 − 9 =
  7. 7.92 − 19 =
  8. 8.565 + 99 =
  9. 9.458 − 99 =
  10. 10.46 + 29 =
  11. 11.50 − 19 =
  12. 12.84 − 9 =
  13. 13.37 − 9 =
  14. 14.33 + 19 =
  15. 15.800 + 99 =
  16. 16.489 − 99 =
  17. 17.48 + 19 =
  18. 18.57 + 9 =
  19. 19.51 + 19 =
  20. 20.82 − 19 =
  21. 21.27 + 9 =
  22. 22.31 + 29 =
  23. 23.21 + 9 =
  24. 24.54 − 29 =
  25. 25.62 + 19 =
  26. 26.885 − 99 =
  27. 27.62 + 29 =
  28. 28.385 + 99 =
  29. 29.41 + 19 =
  30. 30.56 + 19 =
  31. 31.471 + 99 =
  32. 32.66 + 29 =
  33. 33.20 + 9 =
  34. 34.102 − 29 =
  35. 35.17 − 9 =
  36. 36.24 + 9 =
  37. 37.77 + 29 =
  38. 38.45 − 9 =
  39. 39.133 + 99 =
  40. 40.17 + 29 =

Answer key

  1. 36
  2. 5
  3. 554
  4. 20
  5. 6
  6. 21
  7. 73
  8. 664
  9. 359
  10. 75
  11. 31
  12. 75
  13. 28
  14. 52
  15. 899
  16. 390
  17. 67
  18. 66
  19. 70
  20. 63
  21. 36
  22. 60
  23. 30
  24. 25
  25. 81
  26. 786
  27. 91
  28. 484
  29. 60
  30. 75
  31. 570
  32. 95
  33. 29
  34. 73
  35. 8
  36. 33
  37. 106
  38. 36
  39. 232
  40. 46

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