Question 1063633
Q:
A box contains 4 red balls and 6 blue balls. A second box contains 16
red balls and an unknown number of blue balls. A single ball is drawn
from each box. The probability that both balls are of the same color is
0.44. How many blue balls are there in the second box? 
Please explain. 

Tutorial:
Let x = number of blue balls in the 2nd box.

P(BB) + P(RR) = {{{(6/10)(x/(x+16)) + (4/10)(16/(x+16)) = 0.44}}}
Multiply both sides by 100(x+16)
60x + 640 = 44(x + 16)
60x + 640 = 44x + 704
16x = 64
x = 4
There are {{{highlight(4)}}} blue balls in the 2nd box.