class 11 math answer
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7.4 exercise is the points of the all explained
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ANSWER-3
A chord is obtained by joining any two points on a circle. Therefore, total number of chords drawn through 21 points is same as the number of ways of selecting 2 points out of 21 points. This can be done in 21C² ways.
Hence, total number of chords = ²¹C2=
21!/19!2! =21×10=210
ANSWER-5
There are a total of 6 red balls, 5 white balls, and 5 blue balls.
9 balls have to be selected in such a way that each selection consists of 3 balls of each colour.
Here,
3 balls can be selected from 6 red balls in
⁶C3 Ways
3 balls can be selected from 5 white balls
⁵C3
3 balls can be selected from 5 blue balls
⁵C3 Ways
Thus, by multiplication principle, required number of ways of selecting 9 balls
Answer 4 ang 5 question is countinue in the pics
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