Question

Number of 6-digit telephone numbers, which can be constructed with digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, if each number starts with 35 and no digit appears more than once is

• A. $1680$
• B. $8!$
• C. $6!$
• D. $6.6!$

Answer 1

The correct option is A $1680$

$0,1,2,3,4,5,6,7,8,9$

$6$ digit telephone number

first two digits are $3,5$

for rest $4$ blanks there are $8$ possible digits

${=}^8{P}_4$

$=8\times 7\times 6\times 5$

$=1680ways$

$option:A$