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# Need clarity, kindly explain! Suppose that 20 pillars of the same height have been erected along the boundaryof a circular stadium. If the top of each pillar has been connected by beams with thetop of all its non-adjacent pillars, then the total numb

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 :

• Option 1)

170

• Option 2)

180

• Option 3)

210

• Option 4)

190

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Any two non-adjacent pillars are joined by beams.

$\therefore$ no. of beams = no. of diagonals

$=^{20}C_2-20$

$=\frac{20\times 19}{2}-20$

$=190-20$

$=170$

Option (1) is correct.

Option 1)

170

Option 2)

180

Option 3)

210

Option 4)

190

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