Question

A lot consists of 144 ball pens of which 20 are defective and others are good. Find the probability of a good pen or of a defective pen.
plzz answer this ques. ​

Answer 1

ANSWER:-

No. of good pens = 144 – 20 = 124

No. of detective pens = 20

Total no. of possible outcomes =144 (total no. of pens)

(i) For her to buy it the pen should be a good one.

So, let E = event of buying a pen which is good.

No. of favourable outcomes = 124 (124 good pens)

Probability, P(E) =

$\frac{Number \: of \: favourable \: outcomes}{Total \: number \: of \: outcomes}$

$P(E) = \frac{ \cancel{124}}{ \cancel {144}} = \frac{31}{36}$

(ii) Now, Let E

${</strong><strong>E2</strong><strong>}$

= Event of she not buying a pen as it was a defective one.

$P(</strong><strong>E1</strong><strong>) + P(</strong><strong>E2</strong><strong>) = 1 \\ P(</strong><strong>E2</strong><strong>) = 1 - P(</strong><strong>E1</strong><strong>) \\ P(</strong><strong>E2</strong><strong>) = 1 - \frac{ \cancel{ 31}}{ \cancel{ 36} } = \frac{5}{36}$

Therefore, the probability that she will not buy

$\boxed{ = \frac{5}{36} }$