Question

It is known that $3$ out of $10$ television sets are defective. If $2$ television sets are selected at random from the $10$, what is the probability that $1$ of them is defective?

• A. $7/15$
• B. $1/10$
• C. $1/2$
• D. $1/3$
• E. $1$

Answer 1

The correct option is A $7/15$

• Given that $3$ out of $10$ televisions are defective
• number of ways of selecting $2$ televisions is ${{}^{10}C}_2=45$
• number of ways of selecting $2$ televisions such that $1$ is defective is ${{}^{7}C}_1{{}^{3}C}_1=21$
• Therefore the probability is $21/45=7/15$