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 nonadjacent pillars, then the total number of beams is :
Select the correct option:
A
210
B
180
C
170
D
190
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
$\begin{aligned} \text { Required number of beams } & ={ }^{20} \mathrm{C}_2-20 \\ & =190-20=170\end{aligned}$
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