Carcass wrote:
Attachment:
GRE Which of the following are possible side lengths of triangle CDE.png
Which of the following are possible side lengths of triangle CDE ?
Indicate
all such values.
A. 2, 3, and 4
B. 6, 8, and 10
C. 6, 8, and 14
D. 8, 12, and 16
E. 12, 15, and 20
F. 16, 24, and 32
G. 16, 24, and 40
First recognize that ∆BCA and ∆CDE already have one angle in common (
p°)
Since opposite angles are equal, let's denote the two equal angles below with
red starsIf two triangles have two angles in common, it must be the case that their third angles are equal (since the angles in both triangles must add to 180°)
So let's denote those two equal angles with
blue circlesThis tells us that ∆BCA and ∆CDE are
similar triangles.
So,
the ratio of the side lengths in one triangle must equal the ratio of the side lengths in the other triangleThe side lengths in ∆BCA are 4, 6 and 8
So, for ∆BCA,
shortest side : middle side : longest side must equal
4:6:8Since the two triangles are similar, it must also be the case that, for ∆CDE,
shortest side : middle side : longest side = 4:6:8Now let's check the answer choices to see which ones have ratios equivalent to
4:6:8A. 2, 3, and 4. The ratio 2:3:4 is equivalent to
4:6:8 B. 6, 8, and 10. The ratio 6:8:10 is
NOT equivalent to
4:6:8 C. 6, 8, and 14. The ratio 6:8:14 is
NOT equivalent to
4:6:8 D. 8, 12, and 16. The ratio 8:12:16 is equivalent to
4:6:8 E. 12, 15, and 20. The ratio 12:15:20 is
NOT equivalent to
4:6:8 F. 16, 24, and 32. The ratio 16:24:36 is equivalent to
4:6:8 G. 16, 24, and 4. The ratio 4:16:24 is
NOT equivalent to
4:6:8Answer: A, D, F