A box contains 5 red and k blue balls. A ball is selected at random from the box. If the probability of selecting a blue ball is (frac{2}{3}), find the value of k.
-
A.
5 -
B.
6 -
C.
8 -
D.
10
Correct Answer: Option D
Explanation
(p(blue) = frac{text{no of blue balls}}{text{total no of balls}})
= (frac{2}{3} = frac{k}{k + 5})
(3k = 2(k + 5) implies 3k = 2k + 10)
(3k – 2k = k = 10)