JEE MainMathematicsPermutations and CombinationsMCQ+4 / −1
Line of slope 2 and line of slope intersect at the origin O . In the first quadrant, , are 12 points on line and are 9 points on line . Then the total number of triangles, that can be formed having vertices at three of the 22 points , , is:
- A1026
- B1188
- C1134
- D1080
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Correct answer: C
- Count total points
There are:
- 1 point at the origin
- 12 points on line
- 9 points on line
So total number of points is
If no three points were collinear, the number of triangles would be
- Subtract collinear triples
A triangle cannot be formed if all 3 chosen points are collinear.
The only collinear sets of 3 or more points lie on the two given lines.
On line
Points on are: So there are points on .
Number of ways to choose 3 collinear points from these is
On line
Points on are: So there are points on .
Number of ways to choose 3 collinear points from these is
- Compute number of triangles
Hence total number of triangles is
- Check options
corresponds to Option C.
Therefore, the correct answer is
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