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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 554 · 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. 1.603 + 99 =
  2. 2.18 + 19 =
  3. 3.57 + 29 =
  4. 4.44 − 29 =
  5. 5.36 + 29 =
  6. 6.44 − 9 =
  7. 7.63 − 9 =
  8. 8.47 − 19 =
  9. 9.17 + 9 =
  10. 10.62 − 9 =
  11. 11.34 − 9 =
  12. 12.14 + 29 =
  13. 13.468 + 99 =
  14. 14.46 + 9 =
  15. 15.64 − 29 =
  16. 16.185 + 99 =
  17. 17.84 − 9 =
  18. 18.13 + 19 =
  19. 19.46 + 19 =
  20. 20.31 + 9 =
  21. 21.30 − 9 =
  22. 22.18 + 9 =
  23. 23.595 − 99 =
  24. 24.80 + 29 =
  25. 25.19 + 19 =
  26. 26.27 − 19 =
  27. 27.837 − 99 =
  28. 28.210 + 99 =
  29. 29.168 + 99 =
  30. 30.350 − 99 =
  31. 31.593 − 99 =
  32. 32.97 − 19 =
  33. 33.62 − 29 =
  34. 34.68 − 29 =
  35. 35.16 − 9 =
  36. 36.17 + 19 =
  37. 37.135 + 99 =
  38. 38.33 − 19 =
  39. 39.58 + 9 =
  40. 40.56 + 29 =

Answer key

  1. 702
  2. 37
  3. 86
  4. 15
  5. 65
  6. 35
  7. 54
  8. 28
  9. 26
  10. 53
  11. 25
  12. 43
  13. 567
  14. 55
  15. 35
  16. 284
  17. 75
  18. 32
  19. 65
  20. 40
  21. 21
  22. 27
  23. 496
  24. 109
  25. 38
  26. 8
  27. 738
  28. 309
  29. 267
  30. 251
  31. 494
  32. 78
  33. 33
  34. 39
  35. 7
  36. 36
  37. 234
  38. 14
  39. 67
  40. 85

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