11.3 Pyramids and Cones

Hahahaha…..as if they’d all be that easy!   Triangular pyramid with base area 9 in and height 4 in Hahahaha…..as if they’d all be that easy!

Slant height

  Ex 2) Square pyramid with side length 4 in and slant height 6 in

Ex 4) Find the Volume

Example 5 Find the volume of a cone with radius 7 cm and height 15 cm. Give your answers both in terms of  and rounded to the nearest tenth. Volume of a pyramid Substitute 7 for r and 15 for h. = 245 cm3 ≈ 769.7 cm3 Simplify.

Example 6 Find the volume of a cone. Step 1 Use the Pythagorean Theorem to find the height. 162 + h2 = 342 Pythagorean Theorem h2 = 900 Subtract 162 from both sides. h = 30 Take the square root of both sides.

Example 7 Find the volume of the composite figure. Round to the nearest tenth. The volume of the upper cone is

Find the volume of the composite figure. Round to the nearest tenth. The volume of the cylinder is Vcylinder = r2h = (21)2(35)=15,435 cm3. The volume of the lower cone is The volume of the figure is the sum of the volumes. V = 5145 + 15,435 + 5,880 = 26,460  83,126.5 cm3

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