A five digit number is to be formed using each of the digits 1, 2, 3, 4, 5 and 6 ONLY ONCE. How many numbers can be formed when 1 and 2 are not together ?  Choose the correct choice from the following answers:	A) 48	B) 36	C) 72	D) 60	E) 480
Reqd ways = (Total No. of ways - cases when both 1 and 2 are together)   6 numbers can be arranged in 6 places in 6! ways. Now tie 1 and 2 together so effectively there are 5 nos. they can be arranged in 5! ways. 1 and 2 can be arranged within themselves in 2!ways.   Reqd. Answer = 6! - 5!2! = 720 - (120*2)= 
<gadget id="calculator">720 - (120*2)</gadget>
<output>480</output>
480   Answer: 480
<result>E</result>
A five digit number is to be formed using each of the digits 1, 2, 3, 4, 5 and 6 ONLY ONCE. How many numbers can be formed when 1 and 2 are not together ?