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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 929 · 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. 1.24 − 19 =
  2. 2.54 − 19 =
  3. 3.59 − 9 =
  4. 4.40 + 29 =
  5. 5.884 − 99 =
  6. 6.390 + 99 =
  7. 7.83 − 19 =
  8. 8.18 + 29 =
  9. 9.496 + 99 =
  10. 10.340 − 99 =
  11. 11.50 + 19 =
  12. 12.33 + 19 =
  13. 13.32 + 19 =
  14. 14.873 − 99 =
  15. 15.274 + 99 =
  16. 16.30 + 9 =
  17. 17.354 + 99 =
  18. 18.34 − 19 =
  19. 19.612 + 99 =
  20. 20.45 − 29 =
  21. 21.58 − 29 =
  22. 22.81 − 29 =
  23. 23.73 − 29 =
  24. 24.53 − 9 =
  25. 25.575 − 99 =
  26. 26.26 + 9 =
  27. 27.42 − 29 =
  28. 28.67 + 9 =
  29. 29.69 − 19 =
  30. 30.316 − 99 =
  31. 31.50 + 29 =
  32. 32.25 + 9 =
  33. 33.780 + 99 =
  34. 34.650 − 99 =
  35. 35.42 + 29 =
  36. 36.92 − 29 =
  37. 37.14 − 9 =
  38. 38.153 − 99 =
  39. 39.72 + 9 =
  40. 40.29 + 9 =

Answer key

  1. 5
  2. 35
  3. 50
  4. 69
  5. 785
  6. 489
  7. 64
  8. 47
  9. 595
  10. 241
  11. 69
  12. 52
  13. 51
  14. 774
  15. 373
  16. 39
  17. 453
  18. 15
  19. 711
  20. 16
  21. 29
  22. 52
  23. 44
  24. 44
  25. 476
  26. 35
  27. 13
  28. 76
  29. 50
  30. 217
  31. 79
  32. 34
  33. 879
  34. 551
  35. 71
  36. 63
  37. 5
  38. 54
  39. 81
  40. 38

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