Question

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?

Answer 1

First, we need to figure out the volume of the cylinder that holds the ink.  The formula for the volume of a cylinder is $\pi r^{2} h$

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.

$\pi 0.2^{2} *11.5 = 1.445 cm^{3}$

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 $0.206 cm^{3}$ ink each week.