Latest Elitmus Aptitude Question SOLUTION: There are 15 points in a plane of which 8 of them are on a straight line..then how many 1) straight lines can be formed 2)triangles can be formed 3)difference between them?

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(#M40039200) ELITMUS Numerical Ability question P&c Keep an EYE

There are 15 points in a plane of which 8 of them are on a straight line..then how many
1) straight lines can be formed
2)triangles can be formed
3)difference between them?

Asked In Elitmus Ankit Boae (9 years ago)

Unsolved Read Solution (8)

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Read Solution (8) :

Gaurav Dhimankar  (9 years ago)

Sorry did a Minor Mistake
Corrected Solution:
1) 15C2 - (8C2 - 1) = 15C2 - 8C2 + 1 = 78
2) 15C3 - 8C3 = 399
3) 399 - 78 = 321

Is this solution Helpfull? Yes (42) | No (1)  

Ashish  (9 years ago)

1. 15C2 - 8C2 + 1 = 78
2. For a triangle we need 3 points
15C3 - 8C3 = 399
3. 399 - 78 = 321

Is this solution Helpfull? Yes (7) | No   

Gaurav Dhimankar  (9 years ago)

1) 15C2 - (8C2 - 1) = 15C2 - 8C2 + 1 = 78
2) 15C2 - 8C2 = 77
3) 78 - 77 = 1

Is this solution Helpfull? Yes (2) | No (8)  

Dharmendra Singh  (9 years ago)

2) for triangle need three points take 8 points in straight and 7 points randomly, we can't make triangle two choose three points in 8 points because they are in a line(straight).
so required equation will be
2) 8c2*7c1 + 7c2*8c1 + 7c3 =399
there is also possibility of triangle to choose three points among 7 points they are random so triangle will be formed.

Is this solution Helpfull? Yes (2) | No   

KANHAIYA  (9 years ago)

1) 15C2-8C2+1 = 78
2) 15C3-8C3 = 399
3) 399-78 = 321

Is this solution Helpfull? Yes (1) | No   

AMIT KUMAR  (9 years ago)

1)15c2+8c2-1
2)15c3+8c3
3)1-2

Is this solution Helpfull? Yes | No   

vinita  (9 years ago)

why we are taking (-1) in first step..???any bady tell me

Is this solution Helpfull? Yes | No   

vivek  (8 years ago)

Here we can form a straight line using two points...whether they lie on same line.so total no of straight line would be 15C2= 85.
No of triangles would be 15C3-8C3=399
Finally difference equals to 399-85=314

Is this solution Helpfull? Yes | No   

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