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In a bulb factory there are different kinds of bulbs, what is the prob

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Bunuel
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In a bulb factory there are different kinds of bulbs, what is the prob [#permalink] New post   19 Nov 2019, 01:41
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In a bulb factory there are different kinds of bulbs, what is the probability that a bulb chosen randomly is a halogen?

(1) There are three times as many halogens than any other bulb in the factory.
(2) The ratio between the halogen to all the other bulbs is 2 to 7.


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Re: In a bulb factory there are different kinds of bulbs, what is the prob [#permalink] New post   19 Nov 2019, 02:09
Bunuel wrote:
In a bulb factory there are different kinds of bulbs, what is the probability that a bulb chosen randomly is a halogen?

(1) There are three times as many halogens than any other bulb in the factory.
(2) The ratio between the halogen to all the other bulbs is 2 to 7.


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#1
There are three times as many halogens than any other bulb in the factory.
total bulbs not know
x=3x ; total 3/4 halogen
insufficient
#2
The ratio between the halogen to all the other bulbs is 2 to 7.
H/other = 2/7 so P of halogen ; 2/9
IMO B sufficient
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Re: In a bulb factory there are different kinds of bulbs, what is the prob [#permalink] New post   19 Nov 2019, 02:18
My answer is (D).
(1) There are three times as many halogens than any other bulb in the factory.
This indicates that the ratio between Halogens vs. others is 3:1. Sufficient
(2) It provides the ratio directly. Sufficient.

If my answer is right, though, statement (1) and (2) provides different ratios. In actual GMAT DS questions, (1) and (2) never contradict with each other.
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Re: In a bulb factory there are different kinds of bulbs, what is the prob [#permalink] New post   21 Nov 2019, 06:12
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Bunuel wrote:
In a bulb factory there are different kinds of bulbs, what is the probability that a bulb chosen randomly is a halogen?

(1) There are three times as many halogens than any other bulb in the factory.
(2) The ratio between the halogen to all the other bulbs is 2 to 7.


(1) There are three times as many halogens than any other bulb in the factory. insufic

If h=3, a=1; h/total=3/(1+3)=3/4;
If h=3, a=1, b=1; h/total=3/(1+1+3)=3/5;
Since we don't know how many kinds of bulbs there are, we cannot find the prob.

(2) The ratio between the halogen to all the other bulbs is 2 to 7. sufic

h/others=2/7…others=7h/2…total=h+others;
h/total=h/h+others=h/(h+7h/2)=h/(9h/2)=2/9.

Ans (B)
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Re: In a bulb factory there are different kinds of bulbs, what is the prob [#permalink] New post   22 Dec 2020, 11:44
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: In a bulb factory there are different kinds of bulbs, what is the prob [#permalink]
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