Three people of different age groups are to be seated on a bench. How many different sitting arrangements are possible if oldest must always sit next to youngest ?
Answers: A) 2 B) 4 C) 6 D) 8 E) 10
Consider O and Y one. But, in this arrangement they can sit in two different combinations.   O first and Y second or Y first and O second.   Total we have (O and Y) and third person= 2 arrangements to do.   Total arrangements= 2*2= 
<gadget id="calculator">2*2</gadget>
<output>4</output>
4   4 is the answer
<result>B</result>
Three people of different age groups are to be seated on a bench. How many different sitting arrangements are possible if oldest must always sit next to youngest ?