Question

How many seven-digit numbers are there when 0 and 8 cannot be the leading number?

Answer 1

It is given that leading number cannot be 0 and 8 . So, choices are :

[ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 9 ] i.e 8 choices.

Now, choices of other six digits are [ 0, 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8, 9 ] i.e 10 choices.

So, number of seven digits with given constraint is :

N = 8×10×10×10×10×10×10

N = 8000000

Therefore, seven-digit numbers with given constrain are 8000000.

Hence, this is the required solution.