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  • The number of different ways in which five ‘alike dashes’ and eight ‘alike dots’ can be arranged, using only seven of these ‘dashes’ & ‘dots’ is<

The number of different ways in which five ‘alike dashes’ and eight ‘alike dots’ can be arranged, using only seven of these ‘dashes’ & ‘dots’ is

 

Option: 1 1287

Option: 2 119

Option: 3 120

Option: 4 1235520

Answers (1)

best_answer

 

Number of ways of arranging of objects -

The number of ways of filling n distinct objects at r places = n(n - 1) (n - 2) ... (n - r + 1) = =\frac{n(n-1) (n-2)...(n-r+1)(n-r)!}{(n-r)!}=\frac{n!}{(n-r)!} =\ ^{n}p_{r}=n.\ ^{n-1}p_{r-1}

- wherein

Where r\leq n\ \;and\ \;r\geq0

 

 

^7 C _2 + ^7 C _3 + ^7 C _4 + 7 C_ 5 + 7 C _6 + 7 C _7 = 2 ^7 -8 = 120

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SANGALDEEP SINGH

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