Question

Find the number of 4 - digit numbers that can be formed using the digits 1,2,4,5,6,8
if digits can not be repeated.​

Answer 1

Answer:

I think the no be 8 , 6, 5, 4,

Answer 2

Using permutations and combinations,

Let 'n' be no. of digits given = 5 [five digits given]

and 'r' be no. of digits in forming no.=4 [four digit number]

Therefore,

No. of no.s that can be formed

$= {}^{ n} P_{r} \\ = {}^{ 5} P_{4} \\ = \frac{n!}{(n - r)!} \\ = \frac{5!}{(5 - 4)!} \\ = \frac{5!}{1!} = 120 \: numbers$