OGQR 2020: Question No. 215
If three straight lines intersect at a point as shown in the figure above, what is the value of x?
- x = y = z
- z = 60
Source | OGQR 2020 |
Type | Data Sufficiency |
Topic | Geometry |
Sub-Topic | Lines and Angles |
Difficulty | Easy |
Solution
Steps 1 & 2: Understand Question and Draw Inferences
We are given:
- Three intersecting lines, as shown in the diagram.
- And, the angles between these 3 lines.
We need to find:
- The value of x.
Let us name all the three lines as L1, L2, and L3 as shown:
- One angle between line L1 and L2 is x0.
- Similarly, one angle between line L2 and L3 is z0.
- And, one angle between line L1 and L3 is y0.
- Hence, their vertically opposite angles will also be equal as shown in diagram below.
- Therefore, by applying the property that sum of all the angles around a point is 3600, we can say that:
- 2x + 2y + 2z = 3600
- Or, x + y + z = 1800
To find value of x, we need the value of y and z.
With this understanding, let us now analyse the individual statements.
Step 3: Analyse Statement 1
“x = y = z”
- x + x + x = 1800
- 3x = 1800
- From this equation, we can find the value of x.
Thus, statement 1 is sufficient to answer the question.
Step 4: Analyse Statement 2
“z = 60”
Since we do not know the value of y, we cannot find the value of x.
Thus, statement 2 is not sufficient to answer the question.
Step 5: Combine Both Statements Together (If Needed)
As we could determine the answer from statement 1 individually, this step is not required.
Hence, the correct answer is option A.
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