We must set up a proportion. Since x varies directly with y, when y is multiplied by 2, x is also multiplied by 2. 26 times 2 is 52.

Direct variation:

Let  be the number of pizzas and  be the number of people attending. Because  is directly proportional to , we have

and from the problem

.

Therefore, solving for  we get:

Now solving for ,

Thus, for 18 people 9 pizzas are needed.

Direct proportionality results when two quantities increase or decrease at the same time. In the formula for resistance, , as  increases so too does . The same is true for .  It helps to think of these variables in terms of numbers. When the numerator of this formula is increased and the denominator remains the same, the overall quotient would be larger. The opposite is true if the numerator is decreased and the denominator remains the same (quotient would be smaller).

Direct proportionality means that as one increases so does the other. The equation that is indicative of this statement is the following:

Direct proportionality means you should use the equation 

The question says that the amount of money earned by the business is directly proportional to the number of driveways shoveled so that means y must be the amount of money earned ($3000) and x must be the amount of driveways shoveled (600). Plugging these values into the equation you should get

Solve for k by doing the opposite of what is being done to k on both sides of the equation. Since k is being multiplied by 600 divide both sides by 600

Each driveway earned the snow shoveling business $5

Breaking down the question one small piece at a time:

"The force from gravity () is directly proportional" means that the gravity term is going to be on one side of the proportional symbol, and everything else is going to be on the other side.

"to the inverse...of the distance" means that the distance will be in the denominator.  As distance gets larger, force will get smaller.

"of the square of the distance" means that the distance will be squared.

Putting it all together gives:

Write the direct proportionality relationship.

Assume  represents the time, and the  represents the distance traveled.

Substitute the given information to solve for the  constant.

Divide by five on both sides.

The value of  is:  

Substitute this value back into the direct proportionality relationship.

Substitute seven into the  and simplify.

The answer is:  

Write the formula for direct proportionality.

The distance  is dependent on the time  that the car has traveled.  The variables are directly proportional to each other.

Rewrite the equation in terms of distance and time:

Substitute the known distance and time.

Solve for k by dividing by two.

The equation is:  

Substitute the time  hours to determine the distance traveled.

The car will have traveled  in  hours.

First, let's make the height of the building .  We're looking for a ratio of the height of the object to the length of its shadow.  For the man, we know both of these things, so we can express the ratio:

We don't know the building's height, so let's just use  as a stand-in for the ratio for now.  Also, the length of the building's shadow is the length of the man's shadow plus the distance he is from the building:

We set these ratios equal to each other, and solve:

First, we need to find the radius of Bucket B by setting up a proportion:

Now we can plug the radius into the formula for the volume of a cylinder: