There are 110 people at a meeting. they each shake hands with everyone else. how many handshakes were there?

With the information given we can form an equation

Let n=greatest number of handshakes
n(n+1)/2
109(110)/2
11990/2
5995

There would’ve been 5995 handshakes

The equation n(n+1)/2 can also be used for other problems like this

I hope this helps feel free to ask if you are confused about anything :)

 

41 Km  5 litros

x  Km20 litros

x = 41 · 20 / 5 = 41 · 4 = 164 Km