10th Class Mathematics Probability Question Bank MCQs - Probability

A bag contains 6 green balls and n yellow balls. If probability of drawing a yellow ball is five times that of a green ball, then n is equal to:

A) 10

B) 20

C) 30

D) 40

Correct Answer: C

Solution :

[c] Total number of balls \[=6+n\]

So, the possible number of outcomes \[=6+n\]

Now, P(drawing a green ball) \[=\frac{6}{6+n}\]

also, P(drawing a yellow ball) \[\frac{n}{6+n}\]

According to the question,

\[\frac{n}{6+n}=5\left( \frac{6}{6+n} \right)\,\,\,\,\Rightarrow \,\,\,\,\,n=30\]