You have 10 batteries sitting on your desk, three of which are dead. You choose 2 batteries are random for you calculator. What is the expected number of good batteries that you get?

A) 0

B) 1

C) 1.4

D) 2

Question

Mathematics

Cubby

6 May, 08:39

You have 10 batteries sitting on your desk, three of which are dead. You choose 2 batteries are random for you calculator. What is the expected number of good batteries that you get?

A) 0

B) 1

C) 1.4

D) 2

+3

Answers (1)

Know the Answer?

Will Baker · Answer 1

C) 1.4

Step-by-step explanation:

The probability of choosing 2 good ones is 7/10·6/9 = 42/90.

The probability of choosing 1 good one is 7/10·3/9 + 3/10·7/9 = 42/90.

The probability of choosing 0 good ones is 3/10·2/9 = 6/90

The expected value is the sum of the product of number of good ones and their probability:

... 2·42/90 + 1·42/90 + 0·6/90 = (2+1) ·42/90 = 42/30 = 1.4

You have 10 batteries sitting on your desk, three of which are dead. You choose 2 batteries are random for you calculator. What is the expected number of good batteries that you get?A) 0B) 1C) 1.4D) 2

You have 10 batteries sitting on your desk, three of which are dead. You choose 2 batteries are random for you calculator. What is the expected number of good batteries that you get?

A) 0

B) 1

C) 1.4

D) 2