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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 157 · 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. 1.25 − 19 =
  2. 2.47 + 19 =
  3. 3.47 + 9 =
  4. 4.23 + 29 =
  5. 5.96 − 19 =
  6. 6.40 + 9 =
  7. 7.69 − 19 =
  8. 8.58 + 29 =
  9. 9.82 − 29 =
  10. 10.45 + 9 =
  11. 11.21 − 9 =
  12. 12.665 − 99 =
  13. 13.106 − 29 =
  14. 14.19 − 9 =
  15. 15.765 − 99 =
  16. 16.18 + 29 =
  17. 17.25 + 29 =
  18. 18.27 − 9 =
  19. 19.52 + 19 =
  20. 20.22 + 9 =
  21. 21.343 − 99 =
  22. 22.173 − 99 =
  23. 23.51 + 29 =
  24. 24.28 + 9 =
  25. 25.33 − 29 =
  26. 26.39 − 19 =
  27. 27.74 − 19 =
  28. 28.491 + 99 =
  29. 29.45 + 19 =
  30. 30.77 − 29 =
  31. 31.43 − 29 =
  32. 32.217 − 99 =
  33. 33.586 + 99 =
  34. 34.32 − 19 =
  35. 35.75 − 29 =
  36. 36.71 + 19 =
  37. 37.64 + 19 =
  38. 38.341 + 99 =
  39. 39.20 + 9 =
  40. 40.54 − 29 =

Answer key

  1. 6
  2. 66
  3. 56
  4. 52
  5. 77
  6. 49
  7. 50
  8. 87
  9. 53
  10. 54
  11. 12
  12. 566
  13. 77
  14. 10
  15. 666
  16. 47
  17. 54
  18. 18
  19. 71
  20. 31
  21. 244
  22. 74
  23. 80
  24. 37
  25. 4
  26. 20
  27. 55
  28. 590
  29. 64
  30. 48
  31. 14
  32. 118
  33. 685
  34. 13
  35. 46
  36. 90
  37. 83
  38. 440
  39. 29
  40. 25

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