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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 897 · 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. 1.27 − 19 =
  2. 2.15 + 29 =
  3. 3.57 + 9 =
  4. 4.82 − 29 =
  5. 5.46 − 19 =
  6. 6.20 + 19 =
  7. 7.172 + 99 =
  8. 8.42 + 29 =
  9. 9.56 + 9 =
  10. 10.33 − 9 =
  11. 11.419 + 99 =
  12. 12.152 + 99 =
  13. 13.391 + 99 =
  14. 14.80 − 9 =
  15. 15.520 + 99 =
  16. 16.24 + 29 =
  17. 17.62 + 9 =
  18. 18.282 − 99 =
  19. 19.445 − 99 =
  20. 20.232 + 99 =
  21. 21.277 − 99 =
  22. 22.48 + 29 =
  23. 23.26 − 9 =
  24. 24.343 − 99 =
  25. 25.34 + 29 =
  26. 26.24 − 9 =
  27. 27.310 + 99 =
  28. 28.27 + 29 =
  29. 29.79 − 9 =
  30. 30.444 − 99 =
  31. 31.44 − 9 =
  32. 32.39 − 19 =
  33. 33.43 − 19 =
  34. 34.77 + 19 =
  35. 35.68 + 9 =
  36. 36.104 − 29 =
  37. 37.27 + 9 =
  38. 38.54 + 9 =
  39. 39.639 + 99 =
  40. 40.15 + 9 =

Answer key

  1. 8
  2. 44
  3. 66
  4. 53
  5. 27
  6. 39
  7. 271
  8. 71
  9. 65
  10. 24
  11. 518
  12. 251
  13. 490
  14. 71
  15. 619
  16. 53
  17. 71
  18. 183
  19. 346
  20. 331
  21. 178
  22. 77
  23. 17
  24. 244
  25. 63
  26. 15
  27. 409
  28. 56
  29. 70
  30. 345
  31. 35
  32. 20
  33. 24
  34. 96
  35. 77
  36. 75
  37. 36
  38. 63
  39. 738
  40. 24

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