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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 571 · 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. 1.49 + 19 =
  2. 2.67 − 9 =
  3. 3.140 + 99 =
  4. 4.27 + 9 =
  5. 5.68 + 19 =
  6. 6.47 + 19 =
  7. 7.34 + 19 =
  8. 8.26 + 19 =
  9. 9.471 − 99 =
  10. 10.337 + 99 =
  11. 11.57 + 9 =
  12. 12.550 + 99 =
  13. 13.28 − 9 =
  14. 14.83 − 29 =
  15. 15.53 − 9 =
  16. 16.74 + 9 =
  17. 17.76 − 9 =
  18. 18.40 − 29 =
  19. 19.43 − 19 =
  20. 20.23 + 19 =
  21. 21.357 − 99 =
  22. 22.34 + 29 =
  23. 23.427 + 99 =
  24. 24.22 − 9 =
  25. 25.40 + 29 =
  26. 26.59 + 29 =
  27. 27.23 + 29 =
  28. 28.90 − 19 =
  29. 29.29 + 29 =
  30. 30.93 − 19 =
  31. 31.639 − 99 =
  32. 32.63 − 9 =
  33. 33.570 − 99 =
  34. 34.63 − 19 =
  35. 35.430 − 99 =
  36. 36.24 + 29 =
  37. 37.61 − 19 =
  38. 38.492 − 99 =
  39. 39.507 + 99 =
  40. 40.71 + 19 =

Answer key

  1. 68
  2. 58
  3. 239
  4. 36
  5. 87
  6. 66
  7. 53
  8. 45
  9. 372
  10. 436
  11. 66
  12. 649
  13. 19
  14. 54
  15. 44
  16. 83
  17. 67
  18. 11
  19. 24
  20. 42
  21. 258
  22. 63
  23. 526
  24. 13
  25. 69
  26. 88
  27. 52
  28. 71
  29. 58
  30. 74
  31. 540
  32. 54
  33. 471
  34. 44
  35. 331
  36. 53
  37. 42
  38. 393
  39. 606
  40. 90

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