OG: In the figure shown, is l1 || l2?

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In the figure shown, is l1 || l2?

1. r = s
2. t = u

E

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AbeNeedsAnswers wrote:
Fri Jun 05, 2020 6:15 pm
OG2021DS325.png

In the figure shown, is l1 || l2?

1. r = s
2. t = u

E
Target question: In the figure shown, is l1 || l2 ?

When I SCAN the two statements, I can see that statement 1 tells me about 2 angles created by the intersection of line_1 and line m
And statement 2 tells me about 2 angles created by the intersection of line_2 and line m
Since none of the information relates line_1 and line_2, I’m pretty sure I can identify some cases with conflicting answers to the target question.
So, I’m going to head straight to……

Statements 1 and 2 combined
Key concept: For ANY 2 intersecting lines, the opposite angles will ALWAYS be equal

There are several scenarios that satisfy BOTH statements. Here are two:
Case a:
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In this case, the answer to the target question is YES, of the two lines ARE parallel


Case b:
Image
In this case, the answer to the target question is NO, of the two lines are NOT parallel

Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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