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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 771 · 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. 1.73 − 9 =
  2. 2.67 + 9 =
  3. 3.363 − 99 =
  4. 4.216 + 99 =
  5. 5.235 + 99 =
  6. 6.581 + 99 =
  7. 7.58 + 29 =
  8. 8.709 − 99 =
  9. 9.77 − 19 =
  10. 10.58 − 19 =
  11. 11.156 + 99 =
  12. 12.385 − 99 =
  13. 13.46 − 9 =
  14. 14.69 + 19 =
  15. 15.14 + 19 =
  16. 16.50 + 19 =
  17. 17.103 − 29 =
  18. 18.62 + 19 =
  19. 19.30 − 9 =
  20. 20.42 + 19 =
  21. 21.29 + 9 =
  22. 22.242 − 99 =
  23. 23.51 − 29 =
  24. 24.324 + 99 =
  25. 25.56 − 9 =
  26. 26.208 − 99 =
  27. 27.48 − 29 =
  28. 28.31 + 9 =
  29. 29.159 − 99 =
  30. 30.34 − 29 =
  31. 31.40 − 19 =
  32. 32.292 − 99 =
  33. 33.30 − 19 =
  34. 34.440 − 99 =
  35. 35.56 − 29 =
  36. 36.68 + 9 =
  37. 37.82 − 9 =
  38. 38.74 + 19 =
  39. 39.32 − 9 =
  40. 40.51 − 19 =

Answer key

  1. 64
  2. 76
  3. 264
  4. 315
  5. 334
  6. 680
  7. 87
  8. 610
  9. 58
  10. 39
  11. 255
  12. 286
  13. 37
  14. 88
  15. 33
  16. 69
  17. 74
  18. 81
  19. 21
  20. 61
  21. 38
  22. 143
  23. 22
  24. 423
  25. 47
  26. 109
  27. 19
  28. 40
  29. 60
  30. 5
  31. 21
  32. 193
  33. 11
  34. 341
  35. 27
  36. 77
  37. 73
  38. 93
  39. 23
  40. 32

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