Question

Gopi buys a toy for his son. Shop keeper takes out one toy at random from box of 10 toys containing 3 defective toys and other good ones. Find the probability that the Gopi buys the good toy.

Answer 1

Sample space = Set of all the toys in the box

$\therefore n\left(S\right)=10$

No. of defective toys $=3$

So, no. of non-defective toys $10-3=7$

Let E be the event of taking out a non-defective toy at random from the box.

$\therefore n\left(E\right)=7$

The probability that Gopi buys the toy = Probability that the toy is non-defective=$P\left(E\right)=\frac{n\left(E\right)}{n\left(S\right)}=\frac{7}{10}=0.7$