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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 65 · 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. 1.745 + 99 =
  2. 2.241 + 99 =
  3. 3.77 − 19 =
  4. 4.29 − 9 =
  5. 5.142 + 99 =
  6. 6.33 − 19 =
  7. 7.71 + 19 =
  8. 8.397 − 99 =
  9. 9.82 − 9 =
  10. 10.203 + 99 =
  11. 11.360 − 99 =
  12. 12.78 + 9 =
  13. 13.37 − 19 =
  14. 14.15 + 9 =
  15. 15.63 + 29 =
  16. 16.389 − 99 =
  17. 17.42 + 9 =
  18. 18.35 − 9 =
  19. 19.880 − 99 =
  20. 20.78 + 29 =
  21. 21.518 + 99 =
  22. 22.624 + 99 =
  23. 23.18 + 9 =
  24. 24.62 − 29 =
  25. 25.173 + 99 =
  26. 26.202 − 99 =
  27. 27.445 + 99 =
  28. 28.313 + 99 =
  29. 29.25 + 29 =
  30. 30.34 − 29 =
  31. 31.577 − 99 =
  32. 32.102 − 29 =
  33. 33.417 + 99 =
  34. 34.41 + 19 =
  35. 35.27 − 9 =
  36. 36.45 + 9 =
  37. 37.67 − 19 =
  38. 38.62 − 9 =
  39. 39.76 − 29 =
  40. 40.94 − 29 =

Answer key

  1. 844
  2. 340
  3. 58
  4. 20
  5. 241
  6. 14
  7. 90
  8. 298
  9. 73
  10. 302
  11. 261
  12. 87
  13. 18
  14. 24
  15. 92
  16. 290
  17. 51
  18. 26
  19. 781
  20. 107
  21. 617
  22. 723
  23. 27
  24. 33
  25. 272
  26. 103
  27. 544
  28. 412
  29. 54
  30. 5
  31. 478
  32. 73
  33. 516
  34. 60
  35. 18
  36. 54
  37. 48
  38. 53
  39. 47
  40. 65

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