TXTDryFly wrote:

The area of the right triangle ABC is 4 times greater than the area of the right triangle KLM. If the hypotenuse KL is 10 inches, what is the length of the hypotenuse AB?

“INSERT A DRAWING OF TWO RIGHT TRIANGLES”

(1) Angles ABC and KLM are each equal to 55 degrees.

(2) LM is 6 inches.

“INSERT A DRAWING OF TWO RIGHT TRIANGLES”

I thought the answer was D because Statement 1 tells us that the triangles are similar and statement 2 tells us that KLM = a right 6-8-10 triangle. So the area of KLM is 24 which would make ABC’s area = 96 and which makes ABC = 12-16-20 triangle.

The above solution is not right.

Properties of Similar Triangles:• Corresponding angles are the same.

• Corresponding sides are all in the same

proportion.

• It is only necessary to determine that two sets of angles are identical in order to conclude that two triangles are similar; the third set will be identical because all of the angles of a triangle always sum to 180º.

• In similar triangles, the sides of the triangles are in some proportion to one another. For example, a triangle with lengths 3, 4, and 5 has the same angle measures as a triangle with lengths 6, 8, and 10. The two triangles are similar, and all of the sides of the larger triangle are twice the size of the corresponding legs on the smaller triangle.

• If two similar triangles have sides in the ratio

\frac{x}{y}, then their areas are in the ratio

\frac{x^2}{y^2}.

OR in another way: in two similar triangles, the ratio of their areas is the square of the ratio of their sides:

\frac{AREA}{area}=\frac{SIDE^2}{side^2}.

For more on triangles please check Triangles chapter of the Math Book (link in my signature).

Back to original question:

The area of the right triangle ABC is 4 times greater than the area of the right triangle KLM. If the hypotenuse KL is 10 inches, what is the length of the hypotenuse AB? (1) Angles ABC and KLM are each equal to 55 degrees --> ABC and KLM are similar triangles -->

\frac{AREA_{ABC}}{area_{KLM}}=\frac{4}{1}, so the sides are in ratio 2/1 --> hypotenuse KL=10 --> hypotenuse AB=2*10=20. Sufficient.

(2) LM is 6 inches --> KM=8 -->

area_{KLM}=24 -->

AREA_{ABC}=96. But just knowing the are of ABC is not enough to determine hypotenuse AB. For instance: legs of ABC can be 96 and 2 OR 48 and 4 and you'll get different values for hypotenuse. Not sufficient.

Answer: A.

Hope it helps.

_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:

PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.

What are GMAT Club Tests?

25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership