Question

A box contains $40$ red and blue marbles. If a marble is drawn at random, the probability of picking a blue marble is $\frac{3}{8}$. Ansh takes out one red and nine blue marbles and then draws a marble at random. Find the probability of drawing a blue marble

• A. $\frac{4}{5}$
• B. $\frac{2}{5}$
• C. $\frac{7}{40}$
• D. $\frac{1}{5}$

Answer 1

The correct option is D $\frac{1}{5}$

A box contains 40 red and blue marbles. If a marble is drawn at random, the probability of picking a blue marble is $\frac{3}{8}$. Ansh takes out one red and nine blue marbles and then draws a marble at random.

The blue marbles are $N=P\left(E\right)\times$total_marbles = $\frac{3}{8}\ast 40=15$

If he removes $1$ blue and $9$ blue marble then blue marbles are $15-9=6$

and total marbles are $40-10=30$

Hence Probability of finding the blue marble is $P\left(E\right)=\frac{6}{30}=$$\frac{1}{5}$