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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 955 · 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. 1.186 − 99 =
  2. 2.39 − 29 =
  3. 3.59 + 19 =
  4. 4.743 − 99 =
  5. 5.21 + 19 =
  6. 6.613 + 99 =
  7. 7.62 − 19 =
  8. 8.62 + 29 =
  9. 9.17 + 19 =
  10. 10.628 + 99 =
  11. 11.70 − 9 =
  12. 12.50 + 9 =
  13. 13.16 + 29 =
  14. 14.104 − 29 =
  15. 15.66 − 19 =
  16. 16.59 − 29 =
  17. 17.67 + 19 =
  18. 18.31 + 29 =
  19. 19.347 − 99 =
  20. 20.13 + 9 =
  21. 21.80 + 19 =
  22. 22.681 + 99 =
  23. 23.98 − 19 =
  24. 24.74 − 19 =
  25. 25.21 + 29 =
  26. 26.194 + 99 =
  27. 27.12 + 29 =
  28. 28.50 − 29 =
  29. 29.34 − 19 =
  30. 30.69 − 29 =
  31. 31.37 − 19 =
  32. 32.57 − 19 =
  33. 33.92 − 29 =
  34. 34.679 + 99 =
  35. 35.512 + 99 =
  36. 36.66 − 29 =
  37. 37.82 − 9 =
  38. 38.44 + 29 =
  39. 39.37 + 29 =
  40. 40.52 + 19 =

Answer key

  1. 87
  2. 10
  3. 78
  4. 644
  5. 40
  6. 712
  7. 43
  8. 91
  9. 36
  10. 727
  11. 61
  12. 59
  13. 45
  14. 75
  15. 47
  16. 30
  17. 86
  18. 60
  19. 248
  20. 22
  21. 99
  22. 780
  23. 79
  24. 55
  25. 50
  26. 293
  27. 41
  28. 21
  29. 15
  30. 40
  31. 18
  32. 38
  33. 63
  34. 778
  35. 611
  36. 37
  37. 73
  38. 73
  39. 66
  40. 71

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