The correct option is C r=4
We know that nPr=n!(n−r)!.
In the above question, it is given that n=10 and we have to find r.
Now, according to the question,
10Pr=5040
⇒10!(10−r)!=5040
⇒10!(10−r)!=10×9×8×7
⇒10×9×8×7×6!(10−r)!=10×9×8×7
⇒6!(10−r)!=1
⇒6!=(10−r)!
⇒6=10−r
⇒r=10−6=4