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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 204 · 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. 1.67 − 9 =
  2. 2.16 + 29 =
  3. 3.34 − 19 =
  4. 4.396 − 99 =
  5. 5.49 + 19 =
  6. 6.59 − 9 =
  7. 7.102 − 29 =
  8. 8.61 + 9 =
  9. 9.96 − 19 =
  10. 10.266 − 99 =
  11. 11.14 + 19 =
  12. 12.173 − 99 =
  13. 13.32 − 29 =
  14. 14.125 + 99 =
  15. 15.12 + 19 =
  16. 16.64 − 29 =
  17. 17.270 + 99 =
  18. 18.646 − 99 =
  19. 19.424 + 99 =
  20. 20.61 + 19 =
  21. 21.656 + 99 =
  22. 22.57 + 9 =
  23. 23.47 + 29 =
  24. 24.16 + 19 =
  25. 25.505 + 99 =
  26. 26.17 + 19 =
  27. 27.26 + 19 =
  28. 28.512 + 99 =
  29. 29.63 + 9 =
  30. 30.45 − 19 =
  31. 31.109 − 29 =
  32. 32.732 − 99 =
  33. 33.234 − 99 =
  34. 34.29 + 29 =
  35. 35.55 + 19 =
  36. 36.265 + 99 =
  37. 37.25 + 9 =
  38. 38.53 + 9 =
  39. 39.21 + 9 =
  40. 40.223 + 99 =

Answer key

  1. 58
  2. 45
  3. 15
  4. 297
  5. 68
  6. 50
  7. 73
  8. 70
  9. 77
  10. 167
  11. 33
  12. 74
  13. 3
  14. 224
  15. 31
  16. 35
  17. 369
  18. 547
  19. 523
  20. 80
  21. 755
  22. 66
  23. 76
  24. 35
  25. 604
  26. 36
  27. 45
  28. 611
  29. 72
  30. 26
  31. 80
  32. 633
  33. 135
  34. 58
  35. 74
  36. 364
  37. 34
  38. 62
  39. 30
  40. 322

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