Question

If a factory that manufactures light bulbs, 0.04% of the bulbs manufactured are defective. It is expected that there will be one defective light bulb in what number of bulbs that are manufactured?

a) 2500
b) 1250
c) 1000
d) 500
e) 250

Answer 1

\[
0.04\%\, n = 1
\]

Answer 2

250 I think would be the answer. @wio

Answer 3

Not 250.

Percent means per centum, or per hundred. So one percent means one in a hundred. Four percent means four in a hundred... but you don't have four percent, you have point zero four percent... so four in how many? Then simplify that.

Answer 4

My apologies but I don't understand quite well how to set this up.
4 in I'm not sure how many.

Answer 5

OK. So how would you get rid of the decimal? Remember that per also means it is a fraction.

Answer 6

wait, would it be 2,500?

Answer 7

Yes. \(\dfrac{.04}{100}\cdot \dfrac{100}{100}=\dfrac{4}{10000}\) so 4 in 10,000 or one in 2,500.

Answer 8

great! Thank you very much for your help! Would you mind helping me on another problem please? If not, it's fine. :)

Answer 9

What is it?

Answer 10

Its another word problem like this one.

Answer 11

Not type... the actual problem. =)

Answer 12

Three students use a computer for a total of 3 hours. If the first student uses the computer 28% of the total time, and the second student uses the computer 52% of the total time, how many minutes does the third student use the computer?

a) 24
b) 30
c) 36
d) 42
e) 50

Answer 13

OK. First, pull out the numbers and try to see how they relate to the answer you need. So, what important numbers do you have?

Answer 14

3 hours, 28% and 52%

Answer 15

Now, you have 3 hours... but what is the answer asking for?

Answer 16

hold for one second please. :)

Answer 17

ok, I am back. Thank you for waiting.

Answer 18

It is asking how much time the third student used the computer for.

Answer 19

But time in what units?

Answer 20

minutes.

Answer 21

So, you have hours but need minutes. Might as well fix that right off.

Answer 22

ok. I'm just a tid bit confused how to set it up.

Answer 23

Well, the total percentage of all three is 100%, right? So, you are given the persentage for two of them. How will you go about finding the percentage of the third?

Answer 24

100-80= 20?

Answer 25

as in 20%...

Answer 26

OK. So you need 20% of 3 hours in minutes.

Answer 27

3 hours in minutes is 180, but I'm not sure we need to convert that.
would 20% turn into .20 ?

Answer 28

You do need to conver the hours, and yes, .2

Answer 29

i keep getting 15 but that would be wrong since it is not on the answer choices..

Answer 30

Seems you are divinding 3 by .2 But a percentage of in this format is multiplied... and remember, you need minutes!

Answer 31

...I honestly don't know. :/ my apologies.

Answer 32

Well, look at this another way. A dollar!

25% of one dolar is .25 * one dollar... or .25 dollars. But we have another word for that. Cents. So 25 cents.

Can you do the same vasic thing with your problem?

Answer 33

24 minutes?

Answer 34

Hmm... what did you multiply to get that?

Answer 35

actally, im completly wrong. I dont know what I did. I need to go do something'very important quickly. I dont know if you will still be on...but I will keep working on this problem.

Answer 36

Let me try a different example. Say I needed to measure 13% of two miles in feet. So, I need to set this up. Well, one mile is 5280 feet. 13% is .13. So I put the whole thing in one equation:

\(2\times 5280\times .13\)

The 2 is the 2 miles.
The 5280 is to get the answer in feet.
The .13 is the 13%.

\(2\times 5280\times .13 = 1372.8\) feet.

You are doing this same thing! Only the numbers you plug in are different. The basic equation is the same.