Question

A box contains six 40 – W bulbs, five 60 – W bulbs,
and four 75 – W bulbs. If bulbs are selected one by one
in random order, what is the probability that at least
two bulbs must be selected to obtain one that is rated
75 – W?

Answer 1

Answer:

Probability of six 40 watt bulbs

6/15*100=40%

Probability of five 60 watt bulbs

5/15*100=100/3%(Devide it to get the answer on decimal form)

Probabilty of four 75 watt bulbs

4/15*100=80/3%(Devide it to get the answer in decimal form)

Answer 2

Given:

The number of $40W$ bulbs = $6$

The number of $60W$ bulbs = $5$

The number of $75W$ bulbs = $4$

To find:

P (At least  $2$ bulbs must be selected to obtain one that is rated  $75W$)

Step-by-step explanation:

Let us consider $A_{1}$ as At least  $2$ bulbs must be selected to obtain one that is rated  $75W$

$\overline{A_1}$ = Just one bulb was selected which is rated $75W$

$P(A_1)\;=\;1\;-\;P(\overline{A_1})$

$P(A_1)\;=\;1\;-\;\frac4{6+5+4}$

$P(A_1)\;=\;1\;-\;\frac4{15}$

$P(A_1)\;=\;\frac{11}{15}$

Answer:

Therefore, the probability that at least  $2$ bulbs must be selected to obtain one that is rated  $75W$ is $\frac{11}{15}$