Question

A box contains 20 blue and 20 red chips. A chip is drawn and then replaced. Then another chip is drawn. What is the probability that 2 blue chips will be drawn?

A. 1/2

B.1/3

C.1/4

D. 2/3

Answer 1

A box contains 20 blue chips and 20 red chips. That is it contains actually 40 chips.

A chip is drawn and then replaced, so the sample size remains the same.

Suppose we draw first chip. we have total 40 chips in a box out of which 20 are blue chips.

So P( getting first blue chip )= 20/40 =1/2

and after first draw we are replacing it in box again, so we have total 40 chips in a box and 20 blue chips.

P( getting second blue chip )= 20/40 = 1/2

Therefore P( getting 2 blue chips ) = P( getting first blue chip ) * P( getting second blue chip)

= (1/2)* (1/2)

= 1/4

Hence C) 1/4 is correct answer.

Hope this will help you. Thank you :)