At the end of a business conference the ten people present all shake hands with each other once. How many handshakes will there be altogether ?
Choices:
A) 20  B) 45  C) 55  D) 90  E) 85
Explanation:   Clearly, total number of handshakes = (9+ 8 + 7 + 6 + 5 + 4 + 3 + 2+1)= 
<gadget id="calculator">(9+ 8 + 7 + 6 + 5 + 4 + 3 + 2+1)</gadget>
<output>45</output>
45.   Answer: 45
<result>B</result>
At the end of a business conference the ten people present all shake hands with each other once. How many handshakes will there be altogether ?