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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 167 · 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. 1.249 + 99 =
  2. 2.615 − 99 =
  3. 3.68 + 9 =
  4. 4.49 + 29 =
  5. 5.76 − 19 =
  6. 6.257 + 99 =
  7. 7.60 + 29 =
  8. 8.70 − 29 =
  9. 9.110 + 99 =
  10. 10.27 + 9 =
  11. 11.866 − 99 =
  12. 12.84 − 9 =
  13. 13.79 + 9 =
  14. 14.27 + 19 =
  15. 15.32 − 29 =
  16. 16.67 − 19 =
  17. 17.64 − 29 =
  18. 18.374 − 99 =
  19. 19.38 + 19 =
  20. 20.53 + 9 =
  21. 21.268 − 99 =
  22. 22.261 + 99 =
  23. 23.36 − 9 =
  24. 24.46 + 9 =
  25. 25.183 + 99 =
  26. 26.14 + 29 =
  27. 27.541 − 99 =
  28. 28.41 + 19 =
  29. 29.39 + 9 =
  30. 30.71 + 29 =
  31. 31.48 + 19 =
  32. 32.35 + 9 =
  33. 33.23 − 19 =
  34. 34.45 − 29 =
  35. 35.635 + 99 =
  36. 36.181 + 99 =
  37. 37.44 + 19 =
  38. 38.69 + 9 =
  39. 39.62 + 19 =
  40. 40.30 − 9 =

Answer key

  1. 348
  2. 516
  3. 77
  4. 78
  5. 57
  6. 356
  7. 89
  8. 41
  9. 209
  10. 36
  11. 767
  12. 75
  13. 88
  14. 46
  15. 3
  16. 48
  17. 35
  18. 275
  19. 57
  20. 62
  21. 169
  22. 360
  23. 27
  24. 55
  25. 282
  26. 43
  27. 442
  28. 60
  29. 48
  30. 100
  31. 67
  32. 44
  33. 4
  34. 16
  35. 734
  36. 280
  37. 63
  38. 78
  39. 81
  40. 21

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