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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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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%
[Reveal] Spoiler: OA

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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
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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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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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?"

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