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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 234 · 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. 1.18 + 19 =
  2. 2.78 − 19 =
  3. 3.12 + 19 =
  4. 4.375 + 99 =
  5. 5.414 + 99 =
  6. 6.79 + 9 =
  7. 7.618 − 99 =
  8. 8.31 − 9 =
  9. 9.31 + 29 =
  10. 10.64 + 19 =
  11. 11.730 − 99 =
  12. 12.533 + 99 =
  13. 13.77 + 19 =
  14. 14.36 + 9 =
  15. 15.385 + 99 =
  16. 16.63 + 29 =
  17. 17.34 − 19 =
  18. 18.158 + 99 =
  19. 19.40 + 19 =
  20. 20.54 − 29 =
  21. 21.76 − 9 =
  22. 22.22 + 29 =
  23. 23.89 − 9 =
  24. 24.714 + 99 =
  25. 25.855 − 99 =
  26. 26.310 + 99 =
  27. 27.55 + 9 =
  28. 28.60 − 29 =
  29. 29.45 + 19 =
  30. 30.766 + 99 =
  31. 31.23 + 19 =
  32. 32.238 + 99 =
  33. 33.578 − 99 =
  34. 34.46 − 9 =
  35. 35.580 − 99 =
  36. 36.69 − 29 =
  37. 37.30 + 29 =
  38. 38.130 + 99 =
  39. 39.37 − 19 =
  40. 40.77 + 29 =

Answer key

  1. 37
  2. 59
  3. 31
  4. 474
  5. 513
  6. 88
  7. 519
  8. 22
  9. 60
  10. 83
  11. 631
  12. 632
  13. 96
  14. 45
  15. 484
  16. 92
  17. 15
  18. 257
  19. 59
  20. 25
  21. 67
  22. 51
  23. 80
  24. 813
  25. 756
  26. 409
  27. 64
  28. 31
  29. 64
  30. 865
  31. 42
  32. 337
  33. 479
  34. 37
  35. 481
  36. 40
  37. 59
  38. 229
  39. 18
  40. 106

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