Question

bob and bill are planning trips to 4 countries thid year, there are 6 countries they would like to visit they are deciding which countries to skip.a.5b.15c.30d.11

Answer 1

Consider that the number of ways of selecting 'r' objects from 'n' distinct objects is given by,

`^nC_r=\frac{n!}{r!\text{ }.\text{ (n-r)!}}`

There are total 6 countries, out of which 4 is to be selected for the trip.

This means that 2 of the 6 countries have to be skipped.

So the number of ways of selecting 2 countries from 6 countries wull be,

`\begin{gathered} ^6C_2=\frac{6!}{2!\text{ }.\text{ (6-2)!}} \\ ^6C_2=(6*5*4!)/((2*1)*(4!)) \\ ^6C_2=15 \end{gathered}`

Thus, there are 15 ways to select 2 countries which are needed to be skipped.

Therefore, the second option is the correct choice.