Volume of a 3 Dimensional Object Learn how to calculate the volume of a three dimensional, regular shaped solid There are 3 methods that can be used to determine the volume (amount of liquid or amount of space something occupies). We have already talked about one, measuring the volume of a liquid with a graduated cylinder. The other two methods can be used for solids. If the solid has a geometric shape (cube, sphere, etc.), specific measurements can be taken and used in a mathematical formula. The formula for a cubic shape is v = length x width x height or l x w x h. The formula for a cylinder is v = πr2h. Be sure to follow order of operations when using the cylinder formula. There are a few important things to keep in mind when using formulas. 1. Be sure to write the formula out- every time! 2. Be sure all measurements you have taken have the correct number of sig. figs. Record the measurements in place of the letters in the formula. This is called substitution. 3. Calculate the answer, be sure the answer has the correct number of sig. figs and is labeled. If the measurements are taken in centimeters, the label is cm3. Do not consider the value of pi when determining the number of sig. figs. If these steps are not shown, points will be deducted. When measuring a cube, it does not make any difference which side you call the length, width or height since you will be multiplying the measurements. What is important is that you measure each dimension one time. The radius is one half the diameter. If the diameter has 3 sig. figs, be sure the radius has 3 sig. figs. The volume of an irregular shape can also be determined. Place the object in graduated cylinder with a known amount of water. The difference between the original water level and new water level is the volume of the object. 1. What formula is used when determining the volume for a cube or rectangular box? 2. What formula is used when determining the volume of a cylinder? 3. When using the formula for cylinder, what math step should be done first? 4. When determining the volume of a box, does it make any difference which side is called the height or length? 5. Every time a formula is used, 3 steps must be used. List the 3 steps. a. b. c. 6. Write the rule you must follow every time when recording measurements. 7. What place value does each line on a metric ruler represent? What place value will your measurement be recorded to when measuring with a metric ruler? 8. How do you determine where to round your answer to when doing a calculation involving multiplication and division with measurements? Use the website listed if you need more information on this topic. http://www.gradeway.com/lessons/math/findvolume3d.aspx finding volume of solids .