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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 421 · 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. 1.40 − 19 =
  2. 2.32 + 19 =
  3. 3.317 − 99 =
  4. 4.48 + 29 =
  5. 5.73 − 29 =
  6. 6.22 − 19 =
  7. 7.18 + 29 =
  8. 8.38 + 19 =
  9. 9.31 + 9 =
  10. 10.38 − 9 =
  11. 11.41 + 29 =
  12. 12.54 − 9 =
  13. 13.53 + 19 =
  14. 14.30 + 29 =
  15. 15.99 − 19 =
  16. 16.679 + 99 =
  17. 17.132 + 99 =
  18. 18.33 + 9 =
  19. 19.48 + 9 =
  20. 20.338 + 99 =
  21. 21.43 − 29 =
  22. 22.87 − 9 =
  23. 23.27 + 19 =
  24. 24.62 + 19 =
  25. 25.58 − 19 =
  26. 26.69 + 9 =
  27. 27.27 + 29 =
  28. 28.251 − 99 =
  29. 29.81 − 29 =
  30. 30.38 + 29 =
  31. 31.78 + 9 =
  32. 32.31 + 29 =
  33. 33.513 − 99 =
  34. 34.64 − 19 =
  35. 35.48 − 9 =
  36. 36.229 − 99 =
  37. 37.78 − 9 =
  38. 38.34 − 19 =
  39. 39.213 + 99 =
  40. 40.33 − 29 =

Answer key

  1. 21
  2. 51
  3. 218
  4. 77
  5. 44
  6. 3
  7. 47
  8. 57
  9. 40
  10. 29
  11. 70
  12. 45
  13. 72
  14. 59
  15. 80
  16. 778
  17. 231
  18. 42
  19. 57
  20. 437
  21. 14
  22. 78
  23. 46
  24. 81
  25. 39
  26. 78
  27. 56
  28. 152
  29. 52
  30. 67
  31. 87
  32. 60
  33. 414
  34. 45
  35. 39
  36. 130
  37. 69
  38. 15
  39. 312
  40. 4

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