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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 349 · 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. 1.47 + 9 =
  2. 2.322 − 99 =
  3. 3.252 − 99 =
  4. 4.36 − 29 =
  5. 5.54 − 29 =
  6. 6.92 − 29 =
  7. 7.310 − 99 =
  8. 8.123 + 99 =
  9. 9.33 − 29 =
  10. 10.79 − 9 =
  11. 11.37 + 19 =
  12. 12.37 + 9 =
  13. 13.79 + 29 =
  14. 14.614 + 99 =
  15. 15.798 + 99 =
  16. 16.75 − 29 =
  17. 17.34 + 29 =
  18. 18.26 − 9 =
  19. 19.32 − 9 =
  20. 20.254 + 99 =
  21. 21.37 − 19 =
  22. 22.75 + 29 =
  23. 23.65 + 9 =
  24. 24.675 − 99 =
  25. 25.87 − 9 =
  26. 26.24 − 9 =
  27. 27.57 − 9 =
  28. 28.43 − 9 =
  29. 29.219 − 99 =
  30. 30.320 − 99 =
  31. 31.48 + 19 =
  32. 32.99 − 19 =
  33. 33.41 + 19 =
  34. 34.65 − 29 =
  35. 35.16 + 19 =
  36. 36.63 − 19 =
  37. 37.47 − 19 =
  38. 38.68 + 9 =
  39. 39.43 − 29 =
  40. 40.26 + 9 =

Answer key

  1. 56
  2. 223
  3. 153
  4. 7
  5. 25
  6. 63
  7. 211
  8. 222
  9. 4
  10. 70
  11. 56
  12. 46
  13. 108
  14. 713
  15. 897
  16. 46
  17. 63
  18. 17
  19. 23
  20. 353
  21. 18
  22. 104
  23. 74
  24. 576
  25. 78
  26. 15
  27. 48
  28. 34
  29. 120
  30. 221
  31. 67
  32. 80
  33. 60
  34. 36
  35. 35
  36. 44
  37. 28
  38. 77
  39. 14
  40. 35

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