# Thread: trick question for me!!!

1. ## trick question for me!!!

A manufactures of stoves has to buy oven lights from two different because one company cannot meet its demand. The manufacture purchase 60% of the oven lights from company A and the rest from Company B. Past experience shows that 1% of the company’s A’s oven lights are defected and 2.5% of Company’s B lights are defected. Determine the probability that a defective oven light is supplied by company A.

aaaaaaaaaaaaaa I cant get this question to work!!!!

2. Originally Posted by justin
A manufactures of stoves has to buy oven lights from two different because one company cannot meet its demand. The manufacture purchase 60% of the oven lights from company A and the rest from Company B. Past experience shows that 1% of the company’s A’s oven lights are defected and 2.5% of Company’s B lights are defected. Determine the probability that a defective oven light is supplied by company A.

aaaaaaaaaaaaaa I cant get this question to work!!!!
hello,

use a table:
Code:
         A        B
-----|------|-----------
OK  | 99%  |  97.5%
-----|------|-----------
def. |   1% |  2.5%
-----|------|-----------
There are 3.5% defect lights. The probability that one of the defect lights was produced by A is then:

$\displaystyle p(\text{light from A})=\frac{1\%}{3.5\%}\approx 28.6\%$

3. ## thanks!

thank you it makes sense!

4. Originally Posted by earboth
hello,

use a table:
Code:
         A        B
-----|------|-----------
OK  | 99%  |  97.5%
-----|------|-----------
def. |   1% |  2.5%
-----|------|-----------
There are 3.5% defect lights. The probability that one of the defect lights was produced by A is then:

$\displaystyle p(\text{light from A})=\frac{1\%}{3.5\%}\approx 28.6\%$
everyone knows that i'm not that great with probability, so forgive me if this is a silly question. doesn't the fact that $\displaystyle 60 \%$ was supplied by A and $\displaystyle 40 \%$ was supplied by B play any role in the matter? i don't see where you used those facts in the problem.

5. Hello, justin!

Jhevon is right . . . the 60-40 must be included in the problem.
. . and I have a different answer . . .

A maker of stoves has to buy oven lights from two different companies.
The maker buys 60% of the oven lights from company A and the rest from Company B.
Past experience shows that 1% of the company’s A’s oven lights are defective
and 2.5% of Company’s B's lights are defective.
Determine the probability that a defective oven light is supplied by company A.

Suppose 1000 lights are ordered: 600 from company A and 400 from company B.

Since A's light are 1% defective, we can expect: .$\displaystyle 1\% \times 600 \:=\:6$ defective lights in the order.

Since B's lights are 2.5% defective, we can expect: .$\displaystyle 2.5\% \times 400 \:=\:10$ defectives.

In the order, there are 16 defective light ... and 6 are from company A.

Therefore: .$\displaystyle P(\text{company A }|\text{ d{e}f}) \:=\:\frac{6}{16} \;=\;0.375$

6. Originally Posted by Jhevon
everyone knows that i'm not that great with probability, so forgive me if this is a silly question. doesn't the fact that $\displaystyle 60 \%$ was supplied by A and $\displaystyle 40 \%$ was supplied by B play any role in the matter? i don't see where you used those facts in the problem.
Hello, Jhevon,

you are absolutely right. Thanks for looking out.

My apologies!