English

A box contains 2 white balls, 3 black balls and 4 red balls. The number of ways three balls be drawn from the box if at least one black ball is to be included in the draw is ______.

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Question

A box contains 2 white balls, 3 black balls and 4 red balls. The number of ways three balls be drawn from the box if at least one black ball is to be included in the draw is ______.

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Solution

A box contains 2 white balls, 3 black balls and 4 red balls. The number of ways three balls be drawn from the box if at least one black ball is to be included in the draw is 64.

Explanation:

We have 2 white, 3 black and 4 red balls

It is given that atleast 1 black ball is to be included.

∴ Required number of ways = 3C1 × 6C2 + 3C2 × 6C1 + 3C3

= 3 × 15 + 3 × 6 + 1

= 45 + 18 + 1

= 64

Hence, the value of the filler is 64.

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Chapter 7: Permutations and Combinations - Exercise [Page 26]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 7 Permutations and Combinations
Exercise | Q 50 | Page 26

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