Different 37541

There are 15 boys and 20 girls in the brigade. How many different services can be specified if one girl and two boys are on the service?

Correct answer:

n =  2100

Step-by-step explanation:

$$\begin{gathered} C_2(15)=\left(\genfrac{}{}{0ex}{}{15}{2}\right)=\frac{15!}{2!(15-2)!}=\frac{15\cdot 14}{2\cdot 1}=105 \\ n=20\cdot \left(\genfrac{}{}{0ex}{}{15}{2}\right)=20\cdot 105=2100 \end{gathered}$$

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