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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 282 · 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. 1.26 − 9 =
  2. 2.71 + 19 =
  3. 3.22 − 9 =
  4. 4.47 + 19 =
  5. 5.71 − 9 =
  6. 6.676 − 99 =
  7. 7.46 − 19 =
  8. 8.13 + 19 =
  9. 9.73 + 19 =
  10. 10.21 + 29 =
  11. 11.63 + 19 =
  12. 12.44 − 9 =
  13. 13.73 + 29 =
  14. 14.64 + 19 =
  15. 15.108 − 29 =
  16. 16.19 − 9 =
  17. 17.73 − 19 =
  18. 18.54 − 19 =
  19. 19.93 − 19 =
  20. 20.78 + 29 =
  21. 21.18 + 9 =
  22. 22.52 + 19 =
  23. 23.68 − 29 =
  24. 24.53 − 9 =
  25. 25.23 + 19 =
  26. 26.102 − 29 =
  27. 27.112 + 99 =
  28. 28.741 − 99 =
  29. 29.48 − 9 =
  30. 30.268 − 99 =
  31. 31.28 − 19 =
  32. 32.329 + 99 =
  33. 33.23 − 9 =
  34. 34.446 + 99 =
  35. 35.14 − 9 =
  36. 36.380 + 99 =
  37. 37.243 − 99 =
  38. 38.50 − 29 =
  39. 39.528 + 99 =
  40. 40.40 − 9 =

Answer key

  1. 17
  2. 90
  3. 13
  4. 66
  5. 62
  6. 577
  7. 27
  8. 32
  9. 92
  10. 50
  11. 82
  12. 35
  13. 102
  14. 83
  15. 79
  16. 10
  17. 54
  18. 35
  19. 74
  20. 107
  21. 27
  22. 71
  23. 39
  24. 44
  25. 42
  26. 73
  27. 211
  28. 642
  29. 39
  30. 169
  31. 9
  32. 428
  33. 14
  34. 545
  35. 5
  36. 479
  37. 144
  38. 21
  39. 627
  40. 31

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