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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 501 · 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. 1.55 + 9 =
  2. 2.52 + 9 =
  3. 3.43 + 19 =
  4. 4.36 − 19 =
  5. 5.893 − 99 =
  6. 6.74 − 19 =
  7. 7.458 − 99 =
  8. 8.15 + 29 =
  9. 9.329 + 99 =
  10. 10.22 + 9 =
  11. 11.30 + 9 =
  12. 12.54 + 29 =
  13. 13.57 − 29 =
  14. 14.32 + 9 =
  15. 15.53 + 19 =
  16. 16.38 + 9 =
  17. 17.459 + 99 =
  18. 18.35 − 19 =
  19. 19.129 + 99 =
  20. 20.206 + 99 =
  21. 21.196 + 99 =
  22. 22.36 − 9 =
  23. 23.67 + 9 =
  24. 24.19 + 9 =
  25. 25.39 − 19 =
  26. 26.65 − 29 =
  27. 27.68 − 29 =
  28. 28.618 + 99 =
  29. 29.24 + 29 =
  30. 30.237 − 99 =
  31. 31.78 + 29 =
  32. 32.26 − 19 =
  33. 33.755 + 99 =
  34. 34.175 − 99 =
  35. 35.783 − 99 =
  36. 36.389 + 99 =
  37. 37.75 + 19 =
  38. 38.61 + 29 =
  39. 39.45 + 9 =
  40. 40.42 − 29 =

Answer key

  1. 64
  2. 61
  3. 62
  4. 17
  5. 794
  6. 55
  7. 359
  8. 44
  9. 428
  10. 31
  11. 39
  12. 83
  13. 28
  14. 41
  15. 72
  16. 47
  17. 558
  18. 16
  19. 228
  20. 305
  21. 295
  22. 27
  23. 76
  24. 28
  25. 20
  26. 36
  27. 39
  28. 717
  29. 53
  30. 138
  31. 107
  32. 7
  33. 854
  34. 76
  35. 684
  36. 488
  37. 94
  38. 90
  39. 54
  40. 13

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