Question

How many different four digit numbers can be formed using the digits $1,2,3,4,5,6$ when repetition is not allowed and each number starts with $1$?

• A. $60$
• B. $120$
• C. $140$
• D. $25$

Answer 1

The correct option is A $60$

$1,2,3,4,5,6$

No repetition

Four digit number

Starting with $1$

Rest leftover numbers $=5$

Number of blanks $=3$

Number of digits

${}^5{P}_3$
$=5\times 4\times 3$
$=60$