Ifaequals the sum of the even integers from 2 to 40, inclusive, andbequals the sum of the odd integers from 1 to 39, inclusive, what is the value of a - b ?  Pick:
A) 1
B) 10
C) 19
D) 20
E) 21
This is a solution from Beatthegmat:   even numbers:   (40-2)/2 + 1= 
<gadget id="calculator">(40-2)/2 + 1</gadget>
<output>20</output>
20 even integers.   (40+2)/2= 
<gadget id="calculator">(40+2)/2</gadget>
<output>21</output>
21 is the average of the even set.   sum= avg*(#of elements) = 21*20= 
<gadget id="calculator">21*20</gadget>
<output>420</output>
420= a   odd numbers:   (39-1)/2 + 1= 
<gadget id="calculator">(39-1)/2 + 1</gadget>
<output>20</output>
20 odd integers.   (39+1)/2= 
<gadget id="calculator">(39+1)/2</gadget>
<output>20</output>
20 is the average of the odd set.   sum= avg*(#of elements) = 20*20= 
<gadget id="calculator">20*20</gadget>
<output>400</output>
400= b   a-b = 420 - 400= 
<gadget id="calculator">420 - 400</gadget>
<output>20</output>
20.   Answer : 20
<result>D</result>
Ifaequals the sum of the even integers from 2 to 40, inclusive, andbequals the sum of the odd integers from 1 to 39, inclusive, what is the value of a - b ?