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There are many pencils, many erasers, many sharpeners, many sketch pens and many dot pens to choose from upon winning a lottery ticket. What is the number of ways of selecting 18 items in total from them?

Option: 1

7315


Option: 2

7153


Option: 3

18^{5}


Option: 4

Cannot be determined


Answers (1)

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Note the following:

  • The formula for the combination for the selection of the \mathrm{x} items from the \mathrm{y}different items is \mathrm{=^{y}C_{x}=\frac{y!}{x!(y-x)!}}

  • The number of ways of allocating the \mathrm{n} identical items among \mathrm{r} head count with zero, one or more items is \mathrm{=^{n+r-1}C_{r-1}}

As per the available data, the number of varieties of identical items is =1+1+1+1+1=5

Note that the following is evident from the provided data.

  • The number from which the restricted combination is to be made is \mathrm{=n+r-1=18+5-1=22}.

  • The number with which the restricted combination is to be made is \mathrm{=r-1=5-1=4}

Therefore, the required restricted combination is

\mathrm{=^{n+r-1}C_{r-1}}

\mathrm{=^{22}C_{4}}

=\frac{22!}{4!18!}

=7315

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