Find the average of first 20 natural numbers.
Pick:	A) 20.5	B) 18	C) 19.5	D) 10.5	E) 17
Exp. Sum of first n natural numbers = n( n+1)/2   So, sum of first 20 natural numbers = 20*21/2= 
<gadget id="calculator">20*21/2</gadget>
<output>210</output>
210   Required average=210/20= 
<gadget id="calculator">210/20</gadget>
<output>21/2 = around 10.5</output>
10.5   Answer:10.5
<result>D</result>
Find the average of first 20 natural numbers.