McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
2. Surface Areas of Prisms and Cylinders
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Exercise 3 Page 817

Use the formula for the surface area of a prism.

Lateral Area: 288 ft^2
Surface Area: 336 ft^2

Practice makes perfect

We are asked to find the lateral area and surface area of the given prism.

We will do these things one at a time.

Lateral area

Let's recall the formula for the lateral area L of a prism. L=Ph Here, P is the perimeter of the base, and h the height of the prism. Note that the base is a right triangle. We see in the diagram that the lengths of the legs of this triangle are 8ft and 6ft. We can find the hypotenuse by using the Pythagorean Theorem.
c^2 = a^2 + b^2
c^2= 8^2 + 6^2
Solve for c
c^2 = 64 + 36
c^2 = 100
c= 10
Now we know the lengths of the three sides of the base. Let's add them to find its perimeter. P&= 10+ 8+ 6 P&= 24ft Let's now substitute P= 24 and h= 12 in the formula for the lateral area of a prism.
L=Ph
L= 24( 12)
L=288
The lateral area of the solid is 288 ft^2.

Surface Area

Let's recall the formula for the surface area of a prism. S=L+2B Here, L is the lateral area of the prism and B the area of the base. We already know that L=288ft^2. We can calculate the area of the base using the formula for area of a triangle.
B=1/2bh
B=1/2( 6)( 8)
Evaluate right-hand side
B=1/2(48)
B=48/2
B=24
The area of the base is 24ft^2. Now we have enough information to find the surface area of the prism. Let's substitute 288 and 24 for L and B, respectively, into the corresponding formula.
S=L+2B
S=288+2(24)
Evaluate right-hand side
S=288+48
S=336
The surface area of the prism is 336 ft^2.