How many triangles can be obtained by joining 12 points, five of which are collinear?
Answers
Answered by
1
12-5=7
now we have a formula for no. of triangles is
= n(n-1)/2
= 7(7-1)/2= 21 triangles are obtained
now we have a formula for no. of triangles is
= n(n-1)/2
= 7(7-1)/2= 21 triangles are obtained
Answered by
2
Answer:
No of triangle = 210
Step-by-step explanation:
Total no of points = 12
Colinear points = 5
Min. point to form triangle = 3
Hence,
No of triangle = ¹²C³ - ⁵C³
= 12!/3!*9! - 5!/3!*2!
= 12*11*10*9!/3*2*9! - 5*4*3!/3!*2
= 12*11*10/3*2 - 5*4/2
= 11*10*2 - 5*2
= 220 - 10 = 210
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