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06 Jan 2021, 08:57
Kudos
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
80% (01:40) correct
20%
(01:57)
wrong
based on 133
sessions
History
Date
Time
Result
Not Attempted Yet
Eight points lie on the circumference of a circle. What is the positive difference between the number of triangles and the number of quadrilaterals that can be formed by connecting these points?
A. 8
B. 14
C. 56
D. 70
E. 1,344
A. 8
B. 14
C. 56
D. 70
E. 1,344
06 Jan 2021, 14:09
Kudos
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The problem is a Combinations one:
For the Triangles there are 8!/(3!*5!) ways of joining the 8 dots on the circle.
= 56
For the quadrilateral, there are 8!(4!4!) ways of joining the 8 dots on the circle
= 70
The positive difference is therefore (B) 14
06 Jan 2021, 14:21
Kudos
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Given, 8 points were not collinear.
Difference = No. of quadrilaterals - No. of triangles = 8C4 - 8C3 = 70- 56 = 14
So, I think B.
Difference = No. of quadrilaterals - No. of triangles = 8C4 - 8C3 = 70- 56 = 14
So, I think B.
