Question in-tri

4.1 Lines, Angles, and Triangles - Triangle sum theorem
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In triangles A B C and D E F , angles B and E each have measure 27° and angles C and F each have measure 41°. Which additional piece of information is sufficient to determine whether triangle A B C is congruent to triangle D E F ?

A.

The measure of angle A

B.

The length of side A B

C.

The lengths of sides B C and E F

D.

No additional information is necessary.

In triangles A B C and D E F , angles B and E each have

Hard-difficulty · SAT Math · Lines, Angles, and Triangles — Triangle sum theorem. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice C is correct. Since angles B and E each have the same measure and angles C and F each have the same measure, triangles A B C and D E F are similar, where side B C corresponds to side E F . To determine whether two similar triangles are congruent, it is sufficient to determine whether one pair of corresponding sides are congruent. Therefore, to determine whether triangles A B C and D E F are congruent, it is sufficient to determine whether sides B C and E F have equal length. Thus, the lengths of B C and E F are sufficient to determine whether triangle A B C is congruent to triangle D E F .

Choice A is incorrect and may result from conceptual errors.

Choice B is incorrect and may result from conceptual errors.

Choice D is incorrect. The given information is sufficient to determine that triangles A B C and D E F are similar, but not whether they are congruent.