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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 683 · 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. 1.746 − 99 =
  2. 2.80 + 19 =
  3. 3.492 + 99 =
  4. 4.50 − 19 =
  5. 5.42 + 9 =
  6. 6.76 + 19 =
  7. 7.62 + 9 =
  8. 8.44 + 19 =
  9. 9.80 + 9 =
  10. 10.35 − 19 =
  11. 11.44 + 9 =
  12. 12.33 − 9 =
  13. 13.68 + 9 =
  14. 14.19 + 29 =
  15. 15.39 + 9 =
  16. 16.92 − 29 =
  17. 17.280 − 99 =
  18. 18.35 − 9 =
  19. 19.18 + 19 =
  20. 20.44 − 29 =
  21. 21.77 − 9 =
  22. 22.36 − 19 =
  23. 23.66 + 19 =
  24. 24.12 + 29 =
  25. 25.72 + 19 =
  26. 26.27 + 19 =
  27. 27.61 + 9 =
  28. 28.463 − 99 =
  29. 29.160 + 99 =
  30. 30.810 − 99 =
  31. 31.47 − 29 =
  32. 32.24 − 19 =
  33. 33.708 + 99 =
  34. 34.407 − 99 =
  35. 35.108 − 29 =
  36. 36.109 − 29 =
  37. 37.57 + 9 =
  38. 38.79 − 9 =
  39. 39.46 − 9 =
  40. 40.51 − 29 =

Answer key

  1. 647
  2. 99
  3. 591
  4. 31
  5. 51
  6. 95
  7. 71
  8. 63
  9. 89
  10. 16
  11. 53
  12. 24
  13. 77
  14. 48
  15. 48
  16. 63
  17. 181
  18. 26
  19. 37
  20. 15
  21. 68
  22. 17
  23. 85
  24. 41
  25. 91
  26. 46
  27. 70
  28. 364
  29. 259
  30. 711
  31. 18
  32. 5
  33. 807
  34. 308
  35. 79
  36. 80
  37. 66
  38. 70
  39. 37
  40. 22

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