How many different ways can you select a pilot and a co pilot if you have 100 people to choose from?	Choose the correct choice from the following answers
A) 199	B) 200	C) 398	D) 4950	E) 9900
1) PERMUTATION:-   since it is selection, we have to find permutation..   100P2= 100!/(100-2)!=100*99= 
<gadget id="calculator">100*99</gadget>
<output>9_900</output>
9900   2) COMBINATION:-   the ways to select 2 for 2 posts= 100C2   =&gt; 100!/2!98! = 4950   But these 2 can be arranged in 2! ways..   Total= 4950*2= 
<gadget id="calculator">4950*2</gadget>
<output>9_900</output>
9900   3) choose for each post   First post say PILOT can be filled with any of the 100..   co-pilot can be filled by any of the remaining 99   Total= 100*99=9900..   ANS:9900
<result>E</result>
How many different ways can you select a pilot and a co pilot if you have 100 people to choose from?