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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 770 · 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. 1.20 + 19 =
  2. 2.13 + 19 =
  3. 3.48 − 29 =
  4. 4.47 + 9 =
  5. 5.522 + 99 =
  6. 6.32 + 29 =
  7. 7.64 + 9 =
  8. 8.27 + 29 =
  9. 9.76 − 9 =
  10. 10.77 + 9 =
  11. 11.446 + 99 =
  12. 12.62 + 29 =
  13. 13.24 + 19 =
  14. 14.31 + 29 =
  15. 15.655 + 99 =
  16. 16.590 + 99 =
  17. 17.26 − 19 =
  18. 18.39 + 19 =
  19. 19.77 − 29 =
  20. 20.21 + 29 =
  21. 21.90 − 19 =
  22. 22.711 + 99 =
  23. 23.78 + 29 =
  24. 24.48 + 9 =
  25. 25.62 − 29 =
  26. 26.40 + 29 =
  27. 27.77 + 29 =
  28. 28.62 + 9 =
  29. 29.66 + 19 =
  30. 30.34 + 29 =
  31. 31.134 + 99 =
  32. 32.23 + 9 =
  33. 33.12 + 19 =
  34. 34.88 − 9 =
  35. 35.31 + 9 =
  36. 36.31 + 19 =
  37. 37.78 − 19 =
  38. 38.54 + 19 =
  39. 39.363 + 99 =
  40. 40.43 − 19 =

Answer key

  1. 39
  2. 32
  3. 19
  4. 56
  5. 621
  6. 61
  7. 73
  8. 56
  9. 67
  10. 86
  11. 545
  12. 91
  13. 43
  14. 60
  15. 754
  16. 689
  17. 7
  18. 58
  19. 48
  20. 50
  21. 71
  22. 810
  23. 107
  24. 57
  25. 33
  26. 69
  27. 106
  28. 71
  29. 85
  30. 63
  31. 233
  32. 32
  33. 31
  34. 79
  35. 40
  36. 50
  37. 59
  38. 73
  39. 462
  40. 24

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