The portion of a student’s ballpoint pen that contains the ink is a cylinder with a diameter of 0.400 cm and a height of 11.5 cm. if the ink lasts 7 weeks, what is the volume of ink that the student uses each week?

First, we need to figure out the volume of the cylinder that holds the ink.  The formula for the volume of a cylinder is 

We have the diameter, but we can easily find the radius by dividing it by 2.  0.400/2=0.200.  Now, we plug our numbers into the formula.



Now, we need to figure out how much ink he uses each week.  We do this by dividing the volume by the amount of weeks, or 1.445/7 = 0.206.

So, the student uses  ink each week.