Answer:
what i don't understand why you are not answer that question
Step-by-step explanation:

1) This is a combination, so use ⁴⁰C₂.
⁴⁰C₂ = 780
There are 780 handshakes in total.
2) I got my solution by using the combinations formula. Or another way you could do this is to add up... 39 + 38 + 37 + 36 + 35 + 34 + 33 + 32 + 31... +1. You will end up with 780 (I did this to double check my work).
3) The quickest way to figure this out if Drake invited 1,000 people is to use the natural numbers formula = n(n+ 1)/2.
Plug the numbers in: 999(1000)/2 = 499,500
If Drake invited 1,000 people, there would be 499,500 handshakes.
Answer:
The surface area for this cylinder is 252*pi square inches.
Step-by-step explanation:
The surface area of a cylinder can be calculated by using the following formula:
surface area = 2*pi*r² + 2*pi*r*h
Applying the data from the problem, we have:
surface area = 2*pi*(6)² + 2*pi*(6)*15
surface area = 2*pi*36 + 180*pi
surface area = 72*pi + 180*pi
surface area = 252*pi
The surface area for this cylinder is 252*pi square inches.
If this is all the information you have, it is not enough to conclude the region is square. we need more information