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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 785 · 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. 1.13 − 9 =
  2. 2.37 + 29 =
  3. 3.65 + 9 =
  4. 4.72 − 9 =
  5. 5.434 − 99 =
  6. 6.18 + 29 =
  7. 7.75 − 19 =
  8. 8.26 + 29 =
  9. 9.92 − 19 =
  10. 10.15 + 9 =
  11. 11.22 − 9 =
  12. 12.383 − 99 =
  13. 13.62 − 29 =
  14. 14.68 − 9 =
  15. 15.60 − 29 =
  16. 16.61 + 29 =
  17. 17.63 − 9 =
  18. 18.15 + 29 =
  19. 19.17 + 9 =
  20. 20.52 + 9 =
  21. 21.400 − 99 =
  22. 22.40 − 19 =
  23. 23.517 + 99 =
  24. 24.536 − 99 =
  25. 25.107 − 29 =
  26. 26.20 + 19 =
  27. 27.156 + 99 =
  28. 28.514 − 99 =
  29. 29.78 − 9 =
  30. 30.77 + 9 =
  31. 31.45 + 19 =
  32. 32.654 − 99 =
  33. 33.219 + 99 =
  34. 34.86 − 19 =
  35. 35.101 − 29 =
  36. 36.677 + 99 =
  37. 37.46 + 9 =
  38. 38.29 − 19 =
  39. 39.55 − 9 =
  40. 40.99 − 29 =

Answer key

  1. 4
  2. 66
  3. 74
  4. 63
  5. 335
  6. 47
  7. 56
  8. 55
  9. 73
  10. 24
  11. 13
  12. 284
  13. 33
  14. 59
  15. 31
  16. 90
  17. 54
  18. 44
  19. 26
  20. 61
  21. 301
  22. 21
  23. 616
  24. 437
  25. 78
  26. 39
  27. 255
  28. 415
  29. 69
  30. 86
  31. 64
  32. 555
  33. 318
  34. 67
  35. 72
  36. 776
  37. 55
  38. 10
  39. 46
  40. 70

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