Question

7Pr =42, find the value of r

Answer 1

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Answer 2

Answer:

The value of r is 2.

Step-by-step explanation:

Given : $^7P_r=42$

To find : The value of r ?

Solution :

We know that,

$^nP_r=\frac{n!}{(n-r)!}$

Here, n=7

$^7P_r=\frac{7!}{(7-r)!}$

$42=\frac{7\times 6\times 5\times 4\times 3\times 2}{(7-r)!}$

$(7-r)!=\frac{7\times 6\times 5\times 4\times 3\times 2}{42}$

$(7-r)!=5\times 4\times 3\times 2$

$(7-r)!=5!$

$7-r=5$

$r=2$

Therefore, the value of r is 2.