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# In a certain medical survey, 45 percent of the people surveyed had the

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In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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25 Jul 2017, 10:28
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45% (medium)

Question Stats:

66% (01:49) correct 34% (01:56) wrong based on 1106 sessions

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In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

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In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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19 Aug 2017, 14:51
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Quote:
carcass wrote:

In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

dyee630k wrote:
Why can't the trick .45 * .03 be used here?

dyee630k - The key phrasing is not easy to translate.

If you had a Venn diagram, with a circle for A only, a circle for B only, and overlap of A and B, the question asks what percentage of circle "A only" the overlap "A and B" is.

Let's say 100 people, so
45 = A only
3 = A and B

"the percent of those with the type A antigen [45] . . . who also had the type B antigen? [3]" IS WHAT?

Or, "What percent of 45 is 3?"

Or, "3 is what percent of 45?"

The percentage is the variable: ($$\frac{x}{100}$$)(45) = 3

$$\frac{x}{100}$$ = $$\frac{3}{45}$$

45x = 300
x = 6.67

Hope it helps.
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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25 Jul 2017, 22:21
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carcass wrote:
In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

Type A = 45
Type A and B = 3.

The percent of those with the type A antigen who also had the type B antigen $$= \frac{(Type \ A \ and \ B)}{(Type \ A)}*100 = \frac{3}{45}*100 = \frac{20}{3} \approx 6.67%$$.

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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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26 Jul 2017, 15:22
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1
carcass wrote:
In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

We can let the total people = 100. Since 45 percent of them had the type A antigen, we know that 45 of the people had the type A antigen. We also know that 3 percent had both the A and B antigen in their blood. Thus, of the 45 people who had the type A antigen, 3 of them also had the type B antigen. Thus, the percentage is 3/45 x 100% = 6.67%.

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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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19 Aug 2017, 06:49
Why can't the trick .45 * .03 be used here?
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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22 Aug 2017, 17:32
Wow. Yes sorry complete brain fart there. Burnt out but thank you so much. Makes complete sense
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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10 May 2018, 05:02
Bunuel wrote:
carcass wrote:
In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

Type A = 45
Type A and B = 3.

The percent of those with the type A antigen who also had the type B antigen $$= \frac{(Type \ A \ and \ B)}{(Type \ A)}*100 = \frac{3}{45}*100 = \frac{20}{3} \approx 6.67%$$.

Bunuel, Why are we dividing 3 by 45 to find answer? Is the question not asking us to find 3% of 45% and then that represents how much of total as a percent?
Moreover, I am confused whether the question says 3% of 45% or 3% of total?

Do not mean to trouble you.
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Joined: 02 Sep 2009
Posts: 62498
Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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10 May 2018, 21:58
2
1
siddreal wrote:
Bunuel wrote:
carcass wrote:
In a certain medical survey, 45 percent of the people surveyed had the type A antigen in their blood and 3 percent had both the type A antigen and the type B antigen. Which of the following is closest to the percent of those with the type A antigen who also had the type B antigen?

A. 1.35%

B. 6.67%

C. 13.50%

D. 15.00%

E. 42.00%

Type A = 45
Type A and B = 3.

The percent of those with the type A antigen who also had the type B antigen $$= \frac{(Type \ A \ and \ B)}{(Type \ A)}*100 = \frac{3}{45}*100 = \frac{20}{3} \approx 6.67%$$.

Bunuel, Why are we dividing 3 by 45 to find answer? Is the question not asking us to find 3% of 45% and then that represents how much of total as a percent?
Moreover, I am confused whether the question says 3% of 45% or 3% of total?

Do not mean to trouble you.

Say there are 100 people.

45 out of 100 had the type A antigen;
3 out of 100 had both the type A antigen and the type B antigen.

The question asks: what percent of those who had the type A antigen (45) also had the type B antigen (3)? So, what percent of those who had the type A antigen (45) had both (3). Basically we should find what percent is 3 of 45: $$\frac{3}{45}*100$$.
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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02 Aug 2019, 20:57
Why are you dividing (3/45)?? 3 is not a number, but a percent and so is 45. It should be A as .03 times .45 equals 1.35%. As it is 3% of the 45%
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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03 Oct 2019, 05:35
generis wrote:

If you had a Venn diagram, with a circle for A only, a circle for B only, and overlap of A and B, the question asks what percentage of circle "A only" the overlap "A and B" is.

Let's say 100 people, so
45 = A only
3 = A and B

"the percent of those with the type A antigen [45] . . . who also had the type B antigen? [3]" IS WHAT?

Or, "What percent of 45 is 3?"

Or, "3 is what percent of 45?"

The percentage is the variable: ($$\frac{x}{100}$$)(45) = 3

$$\frac{x}{100}$$ = $$\frac{3}{45}$$

45x = 300
x = 6.67

Hope it helps.

Thanks your calculations that helped me find the correct answer. I must differ with your reasoning though since I felt it conflicted with other answers posted here. I'm still trying to draw a Venn diagram with a crossover that you suggested with no luck.

If we say n=100 and assume there is only two types, the two separate inferences that can be made is:

45 people have Type A. (means 55 people must have Type B)

&

3 people have both Types. (means that 97 people have one Type only).

Wouldn't we need two separate Venn diagrams with zero crossover since they are mutually exclusive? Or if we can merge both separate inferences into one Venn diagram, what values would you allocate to each section?

Thanks.
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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10 Oct 2019, 19:14
i feel like this question makes absolutely no sense. how can you take 3% (A&B) of only A (45%).
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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12 Nov 2019, 11:22
1
I couldn't solve it because I failed to grasp the question.
I just couldn't think of what on earth "the percent of those with the type A antigen who also had the type B antigen" means. Poor me!
If it read "what percent of those with the type A antigen is those with both type A and B antigen, it would have been a better prospect for me.

Maybe that's the GMAT's way.
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Re: In a certain medical survey, 45 percent of the people surveyed had the  [#permalink]

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06 Jan 2020, 09:24
Given Type A is of 45%
Both Type A and Type B is of 3%

Asked Percent of Both to type A

3/45*100=1/15*100=0.067*100=6.67
Re: In a certain medical survey, 45 percent of the people surveyed had the   [#permalink] 06 Jan 2020, 09:24
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