Pearson Geometry Common Core, 2011
PG
Pearson Geometry Common Core, 2011 View details
Cumulative Standards Review

Exercise 22 Page 758

Notice that the surface area of one of the halves is the sum of half of the surface area of a cylinder and the area of a rectangle.

≈ 1920 in.^2

Practice makes perfect

We are given that a log is cut lengthwise through its center and we want to find the surface area of one of the halves. To do this let's sketch a diagram of one of the halves.

First let's convert feet to inches, as we want to have all dimensions in the same unit. Recall that there are 12 inches in one foot.

Now let's notice that the surface area of one of the halves is the sum of half of the surface area of a cylinder and the area of a rectangle. 1/2 S.A.+A_r Let's start with evaluating the first part. We will use the fact that the radius is one half of the diameter. 1/2(2π( 182)( 36)+2π ( 182)^2) Let's simplify the above expression.
1/2(2π( 182)(36)+2π ( 182)^2)
Simplify
1/2(2)(π( 182)(36)+π ( 182)^2)
π( 182)(36)+π ( 182)^2
π(9)(36)+π (9)^2
π(9)(36)+π (81)
324π+81π
405π
1272.3450...
≈ 1272
Half of the area of a cylinder is approximately 1272 square inches. Next, let's find the area of a rectangle that has a width of 18 inches and a length of 36 inches. 18* 36=648 The area of the rectangle is 648 square inches. Finally, we will add the half of the surface area and the area of the rectangle. 1272+ 648=1920 The surface area of one of the halves is approximately 1920 square inches.