Given this, what is the probability the two balls were red and blue.
(The answer given was 56/131. I do not understand how did they get there?)
An urn contains 8 red, 7 blue and 5 green balls. Two balls that are of different colours are drawn. ?
2020-09-29 2:09 pm
回答 (1)
2020-09-29 3:14 pm
No. of combinations to draw two balls in different colours
= No. of combinations to draw (red + blue) + (blue + green) + (green + red)
= 8 × 7 + 7 × 5 + 8 × 5
= 56 + 35 + 40
= 131
No. of combinations to draw (red and blue)
= 8 × 7
= 56
P([two balls were red and blue] | [two balls in different colours])
= 56/131
= No. of combinations to draw (red + blue) + (blue + green) + (green + red)
= 8 × 7 + 7 × 5 + 8 × 5
= 56 + 35 + 40
= 131
No. of combinations to draw (red and blue)
= 8 × 7
= 56
P([two balls were red and blue] | [two balls in different colours])
= 56/131
收錄日期: 2021-04-24 08:00:52
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20200929060914AA2flHn