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5c1 + 5c2 + 5c3 + 5c4 +5c5 is Equal to (A) 30 (B) 31 (C) 32 (D) 33

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Question

5C1 + 5C2 5C3 + 5C4 +5C5 is equal to

Options

  • 30

  • 31

  • 32

  • 33

MCQ
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Solution

 31

\[{}^5 C_1 + {}^5 C_2 + {}^5 C_3 + {}^5 C_4 + {}^5 C_5\]
\[= {}^5 C_1 + {}^5 C_2 + {}^5 C_2 +^5 C_1 + {}^5 C_5\]

\[= 2 \times^5 C_1 + 2 \times {}^5 C_2 +^5 C_5 \]
\[ = 2 \times 5 + 2 \times \frac{5!}{2! 3!} + 1 \]
\[ = 10 + 20 + 1 \]
\[ = 31\]

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Chapter 17: Combinations - Exercise 17.5 [Page 25]

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R.D. Sharma Mathematics [English] Class 11
Chapter 17 Combinations
Exercise 17.5 | Q 10 | Page 25

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