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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 574 · 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. 1.44 − 19 =
  2. 2.12 − 9 =
  3. 3.48 + 19 =
  4. 4.27 − 9 =
  5. 5.295 − 99 =
  6. 6.87 − 9 =
  7. 7.27 + 19 =
  8. 8.76 − 9 =
  9. 9.54 + 9 =
  10. 10.278 − 99 =
  11. 11.234 + 99 =
  12. 12.33 − 9 =
  13. 13.75 + 29 =
  14. 14.56 − 29 =
  15. 15.15 − 9 =
  16. 16.38 − 19 =
  17. 17.180 − 99 =
  18. 18.503 + 99 =
  19. 19.76 + 9 =
  20. 20.78 + 19 =
  21. 21.37 − 19 =
  22. 22.93 − 19 =
  23. 23.37 − 29 =
  24. 24.63 + 19 =
  25. 25.19 − 9 =
  26. 26.460 − 99 =
  27. 27.563 − 99 =
  28. 28.489 + 99 =
  29. 29.76 + 29 =
  30. 30.80 + 19 =
  31. 31.732 + 99 =
  32. 32.27 − 19 =
  33. 33.69 + 19 =
  34. 34.79 + 29 =
  35. 35.434 + 99 =
  36. 36.332 − 99 =
  37. 37.34 + 9 =
  38. 38.73 + 9 =
  39. 39.781 − 99 =
  40. 40.40 − 29 =

Answer key

  1. 25
  2. 3
  3. 67
  4. 18
  5. 196
  6. 78
  7. 46
  8. 67
  9. 63
  10. 179
  11. 333
  12. 24
  13. 104
  14. 27
  15. 6
  16. 19
  17. 81
  18. 602
  19. 85
  20. 97
  21. 18
  22. 74
  23. 8
  24. 82
  25. 10
  26. 361
  27. 464
  28. 588
  29. 105
  30. 99
  31. 831
  32. 8
  33. 88
  34. 108
  35. 533
  36. 233
  37. 43
  38. 82
  39. 682
  40. 11

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