Question

how many 5 digit telephone numbers can be constructed using the digits 0 to 9if each number starts with 67 and no digit appears more than once?
plz give a solution

Answer 1

you have 5 digits:
_ _ _ _ _
the first two must be 67
67 _ _ _

Answer 2

k

Answer 3

So now this means u have 1 option for the first number, 1 option for the 2nd number
1*1 _ _ _

Answer 4

Now for the 3rd number we have 8 options (because 6 and 7 were used up and no number can repeat)

Answer 5

k

Answer 6

Following the same idea:
1*1*8*7*6 numbers can be constructed

Answer 7

k i got it.thanx