For any positive integer n, the sum of the first n positive integers equals n(n+1)/2. What is the sum of odd all the integers between 10 and 100?	Pick:
A) 1345	B) 1576	C) 2475	D) 2578	E) 1895
numbers are 11,13,15-------,97,99   Average of the set: (largest+smallest)/2=(99+11)/2= 
<gadget id="calculator">(99+11)/2</gadget>
<output>55</output>
55;   # of terms: (largest-smallest)/2+1=(99-11)/2+1= 
<gadget id="calculator">(99-11)/2+1</gadget>
<output>45</output>
45   The sum= 45*55= 
<gadget id="calculator">45*55</gadget>
<output>2_475</output>
2475   Answer: 2475
<result>C</result>
For any positive integer n, the sum of the first n positive integers equals n(n+1)/2. What is the sum of odd all the integers between 10 and 100?