There are 23 balls in a box: 10 balls are green, 8 are blue and 5 are white. Then 1 green and 1 blue balls are taken from the box and put away. What is the probability that a blue ball is selected at random from the box?	Choose the correct answer
A) 7/21
B) 4/13
C) 3/13
D) 5/13
E) 6/13
If 1 green and 1 blue ball are taken from the box, then there are 9 green, 7 blue and 5 white balls, a total of 21 balls. If one ball is selected at random, the probability that it is blue is given by 7 / 21   7/21nswer : 7/21
<result>A</result>
There are 23 balls in a box: 10 balls are green, 8 are blue and 5 are white. Then 1 green and 1 blue balls are taken from the box and put away. What is the probability that a blue ball is selected at random from the box?