Question

A four digit pin is to be selected using the eight digits 0,1,2,3,4,5,6,7. How many 4 digit pins are possible ?

Answer 1

Given:

The total number digits =8

The number of digits in the pin =4

The number of four-digit pin=

$8C_4=\frac{8!}{4!(8-4)!}$

$=\frac{8!}{4!\times4!}=\frac{8\times7\times6\times5\times4!}{4\times3\times2\times4!}=2\times7\times5=70$

There is 70 possible four-digit pin.