There would be 12 people at the party!
In general, with n+1 people, the number of handshakes is the sum of the first n consecutive numbers: 1+2+3+ ... + n.
Since this sum is n(n+1)/2, we need to solve the equation n(n+1)/2 = 66.
This is the quadratic equation n2+ n -132 = 0. Solving for n, we obtain 11 as the answer and deduce that there were 12 people at the party.
Since 66 is a relatively small number, you can also solve this problem with a hand calculator. Add 1 + 2 = + 3 = +... etc. until the total is 66. The last number that you entered (11) is n.
Hope this helps!
Answer:
-9
Step-by-step explanation:
-1y+11=20
-11= -11
-1y=20-11
-1y=9
-9
The answer is 6 BASED ON PEMDAS
Answer256pi
Step-by-step explanation:
Area=pi*r^2
=pi*16^2
256pi
