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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 373 · 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. 1.747 + 99 =
  2. 2.386 + 99 =
  3. 3.42 + 29 =
  4. 4.52 − 9 =
  5. 5.32 − 29 =
  6. 6.92 − 19 =
  7. 7.27 + 29 =
  8. 8.54 − 19 =
  9. 9.62 − 19 =
  10. 10.24 + 29 =
  11. 11.69 + 29 =
  12. 12.356 − 99 =
  13. 13.448 + 99 =
  14. 14.19 + 29 =
  15. 15.346 − 99 =
  16. 16.54 + 19 =
  17. 17.833 − 99 =
  18. 18.37 − 9 =
  19. 19.18 + 19 =
  20. 20.98 − 19 =
  21. 21.78 − 9 =
  22. 22.512 + 99 =
  23. 23.20 + 9 =
  24. 24.884 − 99 =
  25. 25.13 + 29 =
  26. 26.68 + 29 =
  27. 27.74 + 29 =
  28. 28.638 + 99 =
  29. 29.72 − 19 =
  30. 30.107 − 29 =
  31. 31.90 − 19 =
  32. 32.76 − 9 =
  33. 33.51 − 9 =
  34. 34.64 + 9 =
  35. 35.41 + 29 =
  36. 36.74 − 19 =
  37. 37.106 − 29 =
  38. 38.562 + 99 =
  39. 39.80 + 9 =
  40. 40.23 + 19 =

Answer key

  1. 846
  2. 485
  3. 71
  4. 43
  5. 3
  6. 73
  7. 56
  8. 35
  9. 43
  10. 53
  11. 98
  12. 257
  13. 547
  14. 48
  15. 247
  16. 73
  17. 734
  18. 28
  19. 37
  20. 79
  21. 69
  22. 611
  23. 29
  24. 785
  25. 42
  26. 97
  27. 103
  28. 737
  29. 53
  30. 78
  31. 71
  32. 67
  33. 42
  34. 73
  35. 70
  36. 55
  37. 77
  38. 661
  39. 89
  40. 42

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