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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 991 · 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. 1.17 + 19 =
  2. 2.468 − 99 =
  3. 3.67 − 29 =
  4. 4.73 − 9 =
  5. 5.151 + 99 =
  6. 6.57 + 29 =
  7. 7.793 + 99 =
  8. 8.78 − 19 =
  9. 9.64 − 19 =
  10. 10.700 + 99 =
  11. 11.472 − 99 =
  12. 12.26 − 9 =
  13. 13.469 − 99 =
  14. 14.219 + 99 =
  15. 15.82 − 9 =
  16. 16.13 + 19 =
  17. 17.65 − 29 =
  18. 18.91 − 19 =
  19. 19.87 − 19 =
  20. 20.37 − 9 =
  21. 21.79 + 9 =
  22. 22.12 + 9 =
  23. 23.66 − 19 =
  24. 24.40 − 9 =
  25. 25.48 + 19 =
  26. 26.19 + 19 =
  27. 27.86 − 29 =
  28. 28.800 + 99 =
  29. 29.704 − 99 =
  30. 30.16 − 9 =
  31. 31.347 − 99 =
  32. 32.65 + 19 =
  33. 33.43 + 29 =
  34. 34.92 − 19 =
  35. 35.62 + 9 =
  36. 36.58 − 19 =
  37. 37.61 − 29 =
  38. 38.60 − 29 =
  39. 39.555 + 99 =
  40. 40.102 − 29 =

Answer key

  1. 36
  2. 369
  3. 38
  4. 64
  5. 250
  6. 86
  7. 892
  8. 59
  9. 45
  10. 799
  11. 373
  12. 17
  13. 370
  14. 318
  15. 73
  16. 32
  17. 36
  18. 72
  19. 68
  20. 28
  21. 88
  22. 21
  23. 47
  24. 31
  25. 67
  26. 38
  27. 57
  28. 899
  29. 605
  30. 7
  31. 248
  32. 84
  33. 72
  34. 73
  35. 71
  36. 39
  37. 32
  38. 31
  39. 654
  40. 73

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