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# In the figure above, L2 is perpendicular to L1 . Which of the followi

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Math Expert
Joined: 02 Sep 2009
Posts: 54370
In the figure above, L2 is perpendicular to L1 . Which of the followi  [#permalink]

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19 Jul 2017, 03:26
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15% (low)

Question Stats:

94% (00:35) correct 6% (01:02) wrong based on 53 sessions

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In the figure above, L2 is perpendicular to L1. Which of the following must be true?

I. a = 70
II. If a = 70, then b = 20
III. If b = 20, then a = 70

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II and III

Attachment:

2017-07-19_1425.png [ 10.84 KiB | Viewed 1160 times ]

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Joined: 02 Oct 2015
Posts: 11
Re: In the figure above, L2 is perpendicular to L1 . Which of the followi  [#permalink]

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19 Jul 2017, 03:46
Bunuel wrote:

In the figure above, L2 is perpendicular to L1. Which of the following must be true?

I. a = 70
II. If a = 70, then b = 20
III. If b = 20, then a = 70

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II and III

Attachment:
2017-07-19_1425.png

1) a=70, this could be true, but "a" can take any value between 0 and 90 degrees. False
2) Since "L2" is perpendicular to "L1", then they form a 90 degrees angle, so "a+b" should be always equal to 90, a+b=70+20=90, True
3) Same reasoning as above, a+b=20+70=90. True

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Joined: 06 Nov 2014
Posts: 1877
Re: In the figure above, L2 is perpendicular to L1 . Which of the followi  [#permalink]

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19 Jul 2017, 09:28
Bunuel wrote:

In the figure above, L2 is perpendicular to L1. Which of the following must be true?

I. a = 70
II. If a = 70, then b = 20
III. If b = 20, then a = 70

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II and III

Attachment:
2017-07-19_1425.png

I. a = 70
II. If a = 70, then b = 20
III. If b = 20, then a = 70

Statement 1 may or may not be true always
Statement 2 and 3 will always be true because the sum of a and b will be 90

Correct Option: D
Intern
Joined: 17 Dec 2015
Posts: 17
Re: In the figure above, L2 is perpendicular to L1 . Which of the followi  [#permalink]

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23 Jul 2017, 20:08
Looking at the question. Option 1 can be easily ruled out as angle a can take any value (figure not drawn to scale) ,hence ll and III looks correct. Ans. D.

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Re: In the figure above, L2 is perpendicular to L1 . Which of the followi  [#permalink]

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25 Jul 2017, 11:03
Bunuel wrote:

In the figure above, L2 is perpendicular to L1. Which of the following must be true?

I. a = 70
II. If a = 70, then b = 20
III. If b = 20, then a = 70

(A) I only
(B) II only
(C) III only
(D) II and III only
(E) I, II and III

Using the figure above, we see that a + b = 90.

Let’s analyze each Roman numeral.

I. a = 70

Since we know only that the sum of a and b is 90, we cannot determine whether a = 70. Roman numeral I does not have to be true.

II. If a = 70, then b = 20

Since the sum of a and b is 90, if a = 70, then b = 20. II is true.

III. If b = 20, then a = 70

For the same reasons mentioned in II, III is true.

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Re: In the figure above, L2 is perpendicular to L1 . Which of the followi   [#permalink] 25 Jul 2017, 11:03
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