There are r red ball, b blue ball and w white ball in a bag. What is the ratio of the number of blue ball to the total no. of ball in terms of r, b and w.?  Choose the most appropriate option:
A) r / (r + b + w)  B) r / (r + b)  C) (r + b + w)/r  D) r / (b + w)  E) r * (r + b + w)
The total number of marbles is   r + b + w   The total ratio of blue marbles to the total number of marbles is   r / (r + b + w)   r / (r + b + w)
<result>A</result>
There are r red ball, b blue ball and w white ball in a bag. What is the ratio of the number of blue ball to the total no. of ball in terms of r, b and w.?