JEE PYQ: Permutation And Combination Question 37
Question 37 - 2019 (10 Apr Shift 2)
Suppose that 20 pillars of the same height have been erected along the boundary of a circular stadium. If the top of each pillar has been connected by beams with the top of all its non-adjacent pillars, then the total number of beams is:
(1) 170
(2) 180
(3) 210
(4) 190
Show Answer
Answer: (1)
Solution
Total connections $= {}^{20}C_2 = 190$. Adjacent pairs $= 20$. Beams $= 190 - 20 = 170$.
BETA
