Ask Questions, Get Answers

Want to ask us a question? Click here
Browse Questions
Home  >>  CBSE XI  >>  Math  >>  Permutations and Combinations
0 votes

How many chords can be drawn through 21 points on a circle?

$\begin{array}{1 1}(A)\;200\\(B)\;205\\(C)\;210\\(D)\;215\end{array} $

Can you answer this question?

1 Answer

0 votes
We get a chord by joining two points.If P is the number of chords from 21 points then,
$\Rightarrow \large\frac{21!}{2!19!}$
$\Rightarrow \large\frac{21\times 20(19!)}{2\times 1(19!)}$
$\Rightarrow 21\times 10$
$\Rightarrow 210$ chords
Hence (C) is the correct answer.
answered May 14, 2014 by sreemathi.v

Related questions

Ask Question
student study plans
JEE MAIN, CBSE, AIPMT Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App