Question

The number of permutations of 8 things
taken 'r' at a time is 1680. Then r=
​

Answer 1

Answer:

$8pr = 1680 \\ 8factorial \div rfactorial = 1680 \\ 40320 \div 1680 = rfactorial \\ 24 = rfactorial \\ r = 4$

Answer 2

Answer:

4

Step-by-step explanation:

8pr=1680

8factorial÷rfactorial=1680

40320÷1680=rfactorial

24=rfactorial

r=4