1. Volume of a cylinder is πr^{2}h, volume of a cone is (1/3)nr^{2}h. the trick here is to treat r^{2}h as though it was one value. So, 45n = nr^{2}h means that r^{2}h = 45. Now just plug that in to the cone formula.

2. Using the same formula as above for a cylinder, substitute factors of 2 and 3 in for each respective dimension:

If nr^{2}h = 40 then when you substitute in 2r and 3h you get

n(2r)^{2}(3h) = n(4r^{2})(3h) = 12nr^{2}h

Now just use the original value you got from the question to get the answer.

3. This is similar to number two, use the formula for the volume of a cube and plug in the new dimensions to arrive at the answer:

V_{cube} = l^{3}. The new V = (2l)^{3} = 8l^{3}.

4. This one involves substituting the values given into the equation for the volume of a cone so that you are solving a single equation with one unknown:

(1/3)nr^{2}h = 75n

You're given the radius so all that is left is to plug in the value and solve for h. hope that helped.