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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 879 · 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. 1.27 + 29 =
  2. 2.40 − 9 =
  3. 3.56 + 9 =
  4. 4.367 − 99 =
  5. 5.71 − 29 =
  6. 6.58 + 19 =
  7. 7.489 − 99 =
  8. 8.43 − 29 =
  9. 9.139 + 99 =
  10. 10.41 − 19 =
  11. 11.52 − 29 =
  12. 12.25 − 9 =
  13. 13.39 + 19 =
  14. 14.51 − 19 =
  15. 15.67 + 19 =
  16. 16.171 − 99 =
  17. 17.22 + 9 =
  18. 18.86 − 19 =
  19. 19.13 + 9 =
  20. 20.26 − 19 =
  21. 21.107 − 29 =
  22. 22.48 + 29 =
  23. 23.32 + 9 =
  24. 24.78 + 29 =
  25. 25.64 − 9 =
  26. 26.691 − 99 =
  27. 27.359 − 99 =
  28. 28.66 + 19 =
  29. 29.340 − 99 =
  30. 30.509 + 99 =
  31. 31.333 + 99 =
  32. 32.43 − 19 =
  33. 33.214 + 99 =
  34. 34.43 − 9 =
  35. 35.73 + 29 =
  36. 36.40 − 19 =
  37. 37.76 − 9 =
  38. 38.63 − 9 =
  39. 39.76 − 29 =
  40. 40.76 + 9 =

Answer key

  1. 56
  2. 31
  3. 65
  4. 268
  5. 42
  6. 77
  7. 390
  8. 14
  9. 238
  10. 22
  11. 23
  12. 16
  13. 58
  14. 32
  15. 86
  16. 72
  17. 31
  18. 67
  19. 22
  20. 7
  21. 78
  22. 77
  23. 41
  24. 107
  25. 55
  26. 592
  27. 260
  28. 85
  29. 241
  30. 608
  31. 432
  32. 24
  33. 313
  34. 34
  35. 102
  36. 21
  37. 67
  38. 54
  39. 47
  40. 85

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