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 9 Page 818

Use the formula for the surface area of a prism.

Lateral Area: 24 ft^2
Surface Area: 36 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 4ft and 3ft. We can find the hypotenuse by using the Pythagorean Theorem.
c^2 = a^2 + b^2
c^2= 4^2 + 3^2
Solve for c
c^2 = 16 + 9
c^2 = 25
c= 5
Now we know the lengths of the three sides of the base. Let's add them to find its perimeter. P&= 5+ 4+ 3 P&= 12ft We will now substitute P= 12 and h= 2 in the formula for the lateral area of a prism.
L=Ph
L= 12( 2)
L=24
The lateral area of the solid is 24 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=24ft^2. We can calculate the area of the base using the formula for area of a triangle.
B=1/2bh
B=1/2( 3)( 4)
Evaluate right-hand side
B=12/2
B=6
The area of the base is 6ft^2. Now we have enough information to find the surface area of the prism. Let's substitute 24 and 6 for L and B, respectively, into the corresponding formula.
S=L+2B
S=24+2(6)
Evaluate right-hand side
S=24+12
S=36
The surface area of the prism is 36ft^2.