If all the students in this room shook hands with each other, how many handshakes would there be altogether?
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Topics: Starter  Investigations  Number  Problem Solving
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No. of Students  No. of Handshakes 
1  0 
2  1 
3  3 
4  6 
5  10 
6  15 
7  21 
8  28 
9  36 
10  45 
11  55 
12  66 
13  78 
14  91 
15  105 
16  120 
17  136 
18  153 
19  171 
20  190 
21  210 
22  231 
23  253 
24  276 
25  300 
26  325 
27  351 
28  378 
29  406 
30  435 
31  465 
32  496 
Can you find a formula for the number of handshakes given the number of students?
If instead of handshakes, each student in the room gave every other student a present, how many presents would be given?
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