Recall that the equation for the volume of a sphere is:

For our data, we know:

Solve for . First, multiply both sides by :

Now, divide out the :

Using your calculator, you can solve for . Remember, if need be, you can raise  to the power of  if your calculator does not have a variable-root button.

This gives you:

If you get something like , just round up. This is a rounding issue with some calculators.

Recall that the equation for the volume of a sphere is:

For our data, we know:

Solve for . Begin by dividing out the  from both sides:

Next, multiply both sides by :

Using your calculator, solve for . Recall that you can always use the  power if you don't have a variable-root button.  

You should get:

  If you get , just round up to . This is a general rounding problem with calculators. Since you are looking for the diameter, you must double this to .

Recall that the surface area of a sphere is found by the equation:

For our data, this means:

Solve for . First, divide by :

Take the square root of both sides:

Given the volume of the sphere, , you need to use the formula for volume of a sphere  and work backwards to find the radius. I would multiply both sides by  to get rid of the  in the formula. You then have . Next, divide both sides by  so that all vyou have left is . Finally take the cube root of , to get  units for the radius.

Solving this problem requires recognizing that since the cube is circumscribed by the sphere, both solids share the same center. Now it is just a matter of finding the diagonal of the cube, which will double as the diameter of the sphere (by definition, any straight line which passes through the center of the sphere). The formula for the diagonal of a cube is , where  is the length of the side of a cube. (This occurs because you must use the Pythagorean theorem once for each 2-dimensional "corner" you travel to find the diagonal for a 3-dimensional shape, but for the ACT it's much faster to memorize the formula.)

In this case:

Since the radius is half the diameter, divide the result in half:

1. Use the volume to find the radius:

2. Use the radius to find the diameter:

This question relies on knowledge of the formula for volume of a sphere, which is as follows:  

In this equation, we have two variables,  and . Additionally, we know that  and  is unknown. You can begin by rearranging the volume equation so it is solved for , then plug in  and solve for :

Rearranged form:

Plug in  for V

Simplify the part under the cubed root

1) Cancel the 's since they are in the numerator and denominator.

2) Simplify the fraction and the :

Thus we are left with 

Then, either use your calculator and enter  Or recall that  in order to find that .

We're almost there, but we need to go a step further. Dodge the trap answer "" and carry on. Read the question carefully to see that we need the diameter, not the radius.

So

 is our final answer.

To answer this question, we must calculate the volume of the ball using the equation for the volume of a sphere. The equation for the volume of a sphere is four-thirds multiplied by pi, which is then multiplied by the radius cubed. The equation can be written like this:

We are given the diameter of the sphere in the problem, which is . To get the radius from the diameter, we divide the diameter by . So, for this data:

We can then plug our newly found radius of two into the equation to find the volume. For this data:

We then multiply  by .

We finally substitute 3.14 for pi and multiply again to get our answer.

The question asked us to round to the nearest whole cubic inch. To do this, we round a number up one place if the last digit is a 5, 6, 7, 8, or 9, and we round it down if the last digit is a 1, 2, 3, or 4. Therefore:

Therefore our answer is .

The formula for the volume of a sphere is:

To figure out how far the sphere rolled, we need to know the circumference, so we must first figure out radius. Solve the formula for volume in terms of radius:

Since the answer asks us to round to the nearest integer, we are safe to round  to  at this point.

To find circumference, we now apply our circumference formula:

If our boulder rolled  times, it covered that many times its own circumference.

Thus, our boulder rolled for 

To solve, simply remember that diameter is twice the radius. Don't be fooled when the radius is an algebraic expression and incorporates the arbitrary constant . Thus,