# 7.5 Volume of Prisms and Cylinders

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7.5 Volume of Prisms and Cylinders
MA 08Geometry 7.5 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Goals Find the volume of prisms. Find the volume of cylinders. Solve problems using volume. Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
The number of cubic units contained in a solid. Measured in cubic units. Basic Formula: V = Bh B = area of the base, h = height Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Cubic Unit V = s3 V = 1 cu. unit s 1 1 s 1 s Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Prism: V = Bh B B h h h B Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Cylinder: V = r2h r B h h V = Bh Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Example 1 Find the volume.
Triangular Prism V = Bh Base = 40 V = 40(3) = 120 10 8 3 Abase = ½ (10)(8) = 40 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 3 A soda can measures 4.5 inches high and the diameter is 2.5 inches. Find the approximate volume. V = r2h V = (1.252)(4.5) V  22 in3 (The diameter is 2.5 in. The radius is 2.5 ÷ 2 inches.) Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 4 A wedding cake has three layers. The top cake has a diameter of 8 inches, and is 3 inches deep. The middle cake is 12 inches in diameter, and is 4 inches deep. The bottom cake is 14 inches in diameter and is 6 inches deep. Find the volume of the entire cake, ignoring the icing. Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 4 Solution VTop = (42)(3) = 48  in3 VMid = (62)(4) = 144  in3 VBot = (72)(6) = 294  in3 r = 4 8 3 r = 6 12 4 486  in3 14 6 r = 7 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Concrete Pipe Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 5 A manufacturer of concrete sewer pipe makes a pipe segment that has an outside diameter (o.d.) of 48 inches, an inside diameter (i.d.) of 44 inches, and a length of 52 inches. Determine the volume of concrete needed to make one pipe segment. 48 44 52 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 5 Solution Strategy: Find the area of the ring at the top, which is the area of the base, B, and multiply by the height. View of the Base Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 5 Solution Strategy: Find the area of the ring at the top, which is the area of the base, B, and multiply by the height. Area of Outer Circle: Aout = (242) = 576 Area of Inner Circle: Ain = (222) = 484 Area of Base (Ring): ABase = 576 - 484 = 92 48 44 52 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 5 Solution V = Bh ABase = B = 92 V = (92)(52) V = 4784 V  15,021.8 in3 48 44 52 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 6 4 5 L A metal bar has a volume of 2400 cm3. The sides of the base measure 4 cm by 5 cm. Determine the length of the bar. Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Example 6 Solution 4 5 L V = L  W  H 2400 = L  4  5 2400 = 20L L = 120 cm Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Summary The volumes of prisms and cylinders are essentially the same: V = Bh & V = r2h where B is the area of the base, h is the height of the prism or cylinder. Use what you already know about area of polygons and circles for B. Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
B h h V = r2h V = Bh These are on your reference sheet. Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Which Holds More? This one! 3.2 in 1.6 in 4 in 4.5 in 2.3 in Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
What would the height of cylinder 2 have to be to have the same volume as cylinder 1? r = 3 r = 4 #2 #1 8 h Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Solution r = 4 #1 8 Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

Geometry 12.4 Volume of Prisms and Cylinders
Solution r = 3 #2 h Monday, May 5, 2:51 Geometry 12.4 Volume of Prisms and Cylinders

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