## Math Review – Formulas Chapter Practice Set 3, 8.) “Use Conversion Factors to Rewrite Measurements”.

Practice set three, number eight. How many cubic feet of cement will it
take to make a rec- tangular-shaped driveway that is
forty-five feet long, twelve feet wide, and six inches in depth? Use the formula: “V” equals “L” ” W” “H”. In this formula these letters
represent volume equals length times width times height. I’m asked to find how many cubic feet, so I want to make sure that all of my input measurements are in feet. I have a
diagram given. When I take a look at this I see twelve feet for the width, forty-five feet for the
length but the height is in inches. So let’s
change that. I will use the unit conversion
method. I write down my measurement times a conversion, one foot equals twelve inches. The inches cancel. On my calculator I enter six times one divided by twelve. My answer is a half a foot or point five feet for the thickness. So now let’s use
our formula, volume equals length times width times height. I have forty-five feet times twelve feet times zero point five feet. When I entered this on my calculator
using the multiplication key my answer is two hundred-seventy. And I have feet feet feet, the short abbreviation for that would be cubic feet. In part b, it says since cement is sold by the cubic yard convert
your answer using this conversion factor: one cubic yard equals twenty-seven cubic feet. How I do that is to write down the measurement that I’m starting with, two hundred-seventy cubic feet and then a conversion fraction. One cubic yard equals twenty-seven cubic feet. On my calculator, I enter two seventy times one divided by twenty seven and my answer becomes ten cubic yards. So after this conversion, um, I need ten
cubic yards of cement to make this rectangular driveway.