Given that 24 hours is one full day, we can deduce that 2400 hours is 100 days. One full cycle from that time is equivalent to that time therefore, 2400 hours after 5pm is 5pm.
In this problem it is asking how many gallons the pool holds. It gives you a method of exchange from cubic feet to this however, so in order to solve for this, we first have to solve for how many cubic feet is in the swimming pool, or how much volume the swimming pool has. The formula for the volume of a rectangle is Length*Width*Depth=Volume. Plugging in what we have we get 30*20*6=Volume, or Volume = 3600. As there are 7.5 gallons of water in each cubic foot, we simply multiply 7.5 times 3600 to get the answer. This is 27000.
For this case, the first thing we must do is define variables.
We have then:
x: number of pens
y: number of pencils
We now write the system of inequations:

The solution to the system of inequations is given by the shaded region.
Note: see attached image.
Answer:
C(cone with a radius of 8 units)
Explanation:
When a triangle is spun around its center, it makes a cone (can't make a cylinder because when spun, it doesn't have 2 circular bases). The radius would be 8 because that is what makes the circular base. The 6 is just the height of the triangle and cone once it is spun, it doesn't have anything to do with the base and its radius.