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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 449 · 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. 1.31 + 29 =
  2. 2.46 + 9 =
  3. 3.72 + 9 =
  4. 4.22 + 19 =
  5. 5.93 − 19 =
  6. 6.63 − 19 =
  7. 7.69 − 9 =
  8. 8.229 + 99 =
  9. 9.17 + 19 =
  10. 10.55 + 19 =
  11. 11.47 − 9 =
  12. 12.23 + 19 =
  13. 13.683 − 99 =
  14. 14.391 + 99 =
  15. 15.49 − 29 =
  16. 16.34 + 19 =
  17. 17.27 + 19 =
  18. 18.62 + 19 =
  19. 19.18 + 19 =
  20. 20.58 − 19 =
  21. 21.612 − 99 =
  22. 22.792 − 99 =
  23. 23.853 − 99 =
  24. 24.598 + 99 =
  25. 25.448 − 99 =
  26. 26.42 + 19 =
  27. 27.31 + 19 =
  28. 28.38 − 19 =
  29. 29.281 − 99 =
  30. 30.54 − 29 =
  31. 31.539 + 99 =
  32. 32.64 − 29 =
  33. 33.57 − 19 =
  34. 34.87 − 29 =
  35. 35.51 − 29 =
  36. 36.50 − 9 =
  37. 37.44 − 19 =
  38. 38.295 − 99 =
  39. 39.72 − 19 =
  40. 40.20 − 9 =

Answer key

  1. 60
  2. 55
  3. 81
  4. 41
  5. 74
  6. 44
  7. 60
  8. 328
  9. 36
  10. 74
  11. 38
  12. 42
  13. 584
  14. 490
  15. 20
  16. 53
  17. 46
  18. 81
  19. 37
  20. 39
  21. 513
  22. 693
  23. 754
  24. 697
  25. 349
  26. 61
  27. 50
  28. 19
  29. 182
  30. 25
  31. 638
  32. 35
  33. 38
  34. 58
  35. 22
  36. 41
  37. 25
  38. 196
  39. 53
  40. 11

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