If a equals the sum of the even integers from 2 to 20, inclusive, and b equals the sum of the odd integers from 1 to 19, inclusive, what is the value of a - b ?  Choose the correct choice from the following options: A) 1 B) 10 C) 19 D) 20 E) 21
Sum of consecutive odd or even integers = (no. of odd or even ints) * (first int + last int) / 2   Here A = sum of even ints from 2 to 20, inclusive   number of even ints = 10,   first int + last int = 2+20= 
<gadget id="calculator">2+20</gadget>
<output>22</output>
22   A= 10*22 / 2= 
<gadget id="calculator">10*22 / 2</gadget>
<output>110</output>
110   B= sum of odd ints from 1 to 19, inclusive   number of odd ints = 10,   first int + last int = 1+19= 
<gadget id="calculator">1+19</gadget>
<output>20</output>
20   A= 10*20 / 2= 
<gadget id="calculator">10*20 / 2</gadget>
<output>100</output>
100   A-B= 110 - 100= 
<gadget id="calculator">110 - 100</gadget>
<output>10</output>
10   ANSWER:19
<result>C</result>
If a equals the sum of the even integers from 2 to 20, inclusive, and b equals the sum of the odd integers from 1 to 19, inclusive, what is the value of a - b ?