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# What is area of triangle ABC?

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Manager
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What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 03:20
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72% (00:47) correct 28% (00:40) wrong based on 160 sessions

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What is area of triangle ABC?

A. AC=5
B. Angle ABC=90
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Joined: 30 Aug 2015
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Concentration: Marketing, Finance
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Re: What is area of triangle ABC?  [#permalink]

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20 Feb 2016, 02:04
5
30,60, 90 or think of 45, 45 , 90 both are right angled triangle ...... but with different area
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Manager
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Re: What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 03:22
1
kanigmat011 wrote:
What is area of triangle ABC?

A. AC=5
B. Angle ABC=90

I feel both statements together can give the answer , but official answer states E
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Re: What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 03:49
kanigmat011 wrote:
What is area of triangle ABC?

A. AC=5
B. Angle ABC=90

The answer is straight E. There are infinitely many right triangle with hypotenuse of 5 having different areas.
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Re: What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 04:18
Bunuel wrote:
kanigmat011 wrote:
What is area of triangle ABC?

A. AC=5
B. Angle ABC=90

The answer is straight E. There are infinitely many right triangle with hypotenuse of 5 having different areas.

Hi Brunel,

Can you throw some light on how is that possible.
If hypotenuse is 5 then other two sides needs to be 3 and 4 .
so that would give us the area.
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Re: What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 04:21
kanigmat011 wrote:
Bunuel wrote:
kanigmat011 wrote:
What is area of triangle ABC?

A. AC=5
B. Angle ABC=90

The answer is straight E. There are infinitely many right triangle with hypotenuse of 5 having different areas.

Hi Brunel,

Can you throw some light on how is that possible.
If hypotenuse is 5 then other two sides needs to be 3 and 4 .
so that would give us the area.

Let me ask you how do you know that the sides are 3 and 4? Are we told that the lengths of the sides must be integers? Does x^2 + y^2 = 5^2 have only one solution?
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Re: What is area of triangle ABC?  [#permalink]

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18 Feb 2015, 21:43
2
Hi kanigmat011,

While the 3/4/5 right triangle is a common enough right triangle in the realm of standardized testing (and you'll likely see it -or a multiple of it - at least once on Test Day), if you have just one side of a right triangle, then you have NO WAY of knowing what the other two sides are.

As a question places more and more 'restrictions' into play, then those 'restrictions' might help you to narrow the possibilities down to just one option, but without restrictions, you have to consider more than just the obvious options.

For example:
We're given a right triangle with a hypotenuse of 5 and no other restrictions. Using the Pythagorean Theorem, we have A^2 + B^2 = 5^2. It's POSSIBLE that the other two sides are 3 and 4, but those sides could just as easily be 1 and (root24).

With this same situation, if the prompt included the restriction that the missing sides were both INTEGERS, then the sides would have to be 3 and 4.

Here's another example:
If you have a right triangle and you know that two of the sides are 3 and 4, does the third side have to be 5?....

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Special Offer: Save $75 + GMAT Club Tests Free Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/ Manager Joined: 27 Jul 2014 Posts: 240 Schools: ISB '15 GMAT 1: 660 Q49 V30 GPA: 3.76 Re: What is area of triangle ABC? [#permalink] ### Show Tags 19 Feb 2015, 14:33 EMPOWERgmatRichC wrote: Hi kanigmat011, While the 3/4/5 right triangle is a common enough right triangle in the realm of standardized testing (and you'll likely see it -or a multiple of it - at least once on Test Day), if you have just one side of a right triangle, then you have NO WAY of knowing what the other two sides are. As a question places more and more 'restrictions' into play, then those 'restrictions' might help you to narrow the possibilities down to just one option, but without restrictions, you have to consider more than just the obvious options. For example: We're given a right triangle with a hypotenuse of 5 and no other restrictions. Using the Pythagorean Theorem, we have A^2 + B^2 = 5^2. It's POSSIBLE that the other two sides are 3 and 4, but those sides could just as easily be 1 and (root24). With this same situation, if the prompt included the restriction that the missing sides were both INTEGERS, then the sides would have to be 3 and 4. Here's another example: If you have a right triangle and you know that two of the sides are 3 and 4, does the third side have to be 5?.... GMAT assassins aren't born, they're made, Rich Thanks a lot Rich that really helped Manager Joined: 03 Aug 2015 Posts: 52 Concentration: Strategy, Technology Schools: ISB '18, SPJ GMBA '17 GMAT 1: 680 Q48 V35 What is area of triangle ABC? [#permalink] ### Show Tags 11 Feb 2016, 10:54 EMPOWERgmatRichC wrote: Hi kanigmat011, While the 3/4/5 right triangle is a common enough right triangle in the realm of standardized testing (and you'll likely see it -or a multiple of it - at least once on Test Day), if you have just one side of a right triangle, then you have NO WAY of knowing what the other two sides are. As a question places more and more 'restrictions' into play, then those 'restrictions' might help you to narrow the possibilities down to just one option, but without restrictions, you have to consider more than just the obvious options. For example: We're given a right triangle with a hypotenuse of 5 and no other restrictions. Using the Pythagorean Theorem, we have A^2 + B^2 = 5^2. It's POSSIBLE that the other two sides are 3 and 4, but those sides could just as easily be 1 and (root24). With this same situation, if the prompt included the restriction that the missing sides were both INTEGERS, then the sides would have to be 3 and 4. Here's another example: If you have a right triangle and you know that two of the sides are 3 and 4, does the third side have to be 5?.... GMAT assassins aren't born, they're made, Rich Rich, I believe the answer to this Q is Yes.... The diagonal has to be '5' applying Pythagoras Theorem.......... Kindly clarify.. Thanks, A CEO Joined: 20 Mar 2014 Posts: 2624 Concentration: Finance, Strategy Schools: Kellogg '18 (M) GMAT 1: 750 Q49 V44 GPA: 3.7 WE: Engineering (Aerospace and Defense) Re: What is area of triangle ABC? [#permalink] ### Show Tags 11 Feb 2016, 11:12 2 ArunpriyanJ wrote: EMPOWERgmatRichC wrote: Hi kanigmat011, While the 3/4/5 right triangle is a common enough right triangle in the realm of standardized testing (and you'll likely see it -or a multiple of it - at least once on Test Day), if you have just one side of a right triangle, then you have NO WAY of knowing what the other two sides are. As a question places more and more 'restrictions' into play, then those 'restrictions' might help you to narrow the possibilities down to just one option, but without restrictions, you have to consider more than just the obvious options. For example: We're given a right triangle with a hypotenuse of 5 and no other restrictions. Using the Pythagorean Theorem, we have A^2 + B^2 = 5^2. It's POSSIBLE that the other two sides are 3 and 4, but those sides could just as easily be 1 and (root24). With this same situation, if the prompt included the restriction that the missing sides were both INTEGERS, then the sides would have to be 3 and 4. Here's another example: If you have a right triangle and you know that two of the sides are 3 and 4, does the third side have to be 5?.... GMAT assassins aren't born, they're made, Rich Rich, I believe the answer to this Q is Yes.... The diagonal has to be '5' applying Pythagoras Theorem.......... Kindly clarify.. Thanks, A It is always good to learn the correct terms. It is the 'hypotenuse' in a right angled triangle and NOT a 'diagonal'. The answer to Rich's question is NOT necessarily = 5. You are not told that the 2 sides making the right angle are 3 and 4. What if the hypotenuse of this right triangle = 4 and one of the other sides = 3. Then the 3rd side MUST be = $$\sqrt {7}$$ Hope this helps. Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7252 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: What is area of triangle ABC? [#permalink] ### Show Tags 12 Feb 2016, 05:53 2 Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution. What is area of triangle ABC? A. AC=5 B. Angle ABC=90 In the original condition, for the triangle, there are 3 variables, which should match with the number of equations. So you need 3 equations. For 1) 1 equation, for 2) 1 equation, which is likely to make E the answer. When 1) & 2), you cannot figure out the length of AB and area is not unique, which is not sufficient. Therefore, the answer is E. -> For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D. _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Re: What is area of triangle ABC?  [#permalink]

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Re: What is area of triangle ABC?   [#permalink] 08 Jul 2017, 02:01
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