Variations

Find the number of items when the count of variations of the fourth class without repeating is 42 times larger than the count of variations of the third class without repetition.

Correct answer:

n =  45

Step-by-step explanation:

$$\begin{gathered} V_4(n)=42\cdot V_3(n) \\ n(n-1)(n-2)(n-3)=42\cdot n(n-1)(n-2) \\ (n-3)=42 \\ n=42+3=45 \end{gathered}$$

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