A five digit number is to be formed using each of the digits 1, 2, 3, 4 ONLY ONCE. How many numbers can be formed when 1 and 2 are not together ?	Choose the correct option:
A) 12
B) 36
C) 72
D) 60
E) 120
Reqd ways = (Total No. of ways - cases when both 1 and 2 are together)   4 numbers can be arranged in 4 places in 4! ways. Now tie 1 and 2 together so effectively there are 4 nos. they can be arranged in 3! ways. 1 and 2 can be arranged within themselves in 2!ways.   Reqd. 12nswer = 4! - 3!2! = 24 - (6*2)= 
<gadget id="calculator">24 - (6*2)</gadget>
<output>12</output>
12   12nswer: 12
<result>A</result>
A five digit number is to be formed using each of the digits 1, 2, 3, 4 ONLY ONCE. How many numbers can be formed when 1 and 2 are not together ?