Qr help!!

[flin5845]

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Can someone explain a couple questions.

How many chords on a circle can be drawn from six distinct points lying on the circle.
A. 6
B. 12
C. 15
D. 30
E. 18


Thanks.

 

[FROGGBUSTER]

Can someone explain a couple questions.

How many chords on a circle can be drawn from six distinct points lying on the circle.
A. 6
B. 12
C. 15
D. 30
E. 18


Thanks.

Well basically you're just trying to find how many combinations you can make when you draw 2 things from a bag of 6 things.

So you would just do 6*5 = 30. But this double-counts by a factor of 2, so you would divide by 2 to yield 15. It double-counts because cord A-B is the same as cord B-A.

Hope this helps.

 

[PooyaH]

Can someone explain a couple questions.

How many chords on a circle can be drawn from six distinct points lying on the circle.
A. 6
B. 12
C. 15
D. 30
E. 18


Thanks.

This is what you use for circles and chords:

C[n] = n(n-1)/2, where n is the number of points on a circle.

So the answer would be 15.

 

[NewBee12]

Or you can think of it as a combination problem. In how many ways you can pick 2 out of 6? 2 because 2 points define a chord.
And the answer is 15

 

[wired202808]

Can someone explain a couple questions.

How many chords on a circle can be drawn from six distinct points lying on the circle.
A. 6
B. 12
C. 15
D. 30
E. 18


Thanks.

You have 6 total points but only need 2 points to make a chord i.e. order does not matter

(6*5) / 2 = 15