GED Math : Area

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #1 : Area

Triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram. .  is a right angle. What percent of  has been shaded in?

Possible Answers:

Correct answer:

Explanation:

 is a right triangle with legs ; its area is half the product of its legs, which is

 is a right triangle with legs 

and

 ;

its area is half the product of its legs, which is

The shaded region is the former triangle removed from the latter triangle; its area is the difference of the two: .

This region is therefore

 of .

Example Question #2 : Area

Triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram.  is a right angle. What is the area of the shaded region?

Possible Answers:

Correct answer:

Explanation:

 is a right triangle with legs ; its area is half the product of its legs, which is

 is a right triangle with legs 

and

 ;

its area is half the product of its legs, which is

The shaded region is the former triangle removed from the latter triangle; its area is the difference of the two: .

Example Question #3 : Area

Give the area of a regular hexagon with perimeter 36.

Possible Answers:

Correct answer:

Explanation:

A hexagon has six sides; a regular hexagon with perimeter 36 has sidelength 

.

A regular hexagon can be divided into six triangles, each of which can be easily proved equilateral, as seen in the diagram below:

Hexagon_3

Each equilateral triangle has sidelength 6, so each has area

.

The total area of the hexagon is the area of six such triangles:

Example Question #3 : Area

Hexagon

The above hexagon is regular. Give its area.

Possible Answers:

Correct answer:

Explanation:

A regular hexagon can be divided into six triangles, each of which can be easily proved equilateral, as seen in the diagram below:

Hexagon_2

All segments shown are congruent, and, since the diameter shown in the original diagram is 4, each sidelength is half this, or 2.

Each equilateral triangle has area

.

There are six such triangles, so the total area of the hexagon is six times this, or .

Example Question #4 : Area

Determine the area of a square with a side length of .

Possible Answers:

Correct answer:

Explanation:

Write the area of a square.

Substitute the side into the formula.

The answer is:  

Example Question #5 : Area

Thingy

Figure NOT drawn to scale.

Refer to the above figure. Every angle shown is a right angle.

Give its area.

Possible Answers:

Correct answer:

Explanation:

Examine the bottom figure, in which the bottom two sides have been connected. Note that the figure is now a rectangle cut out of a rectangle, and, since the opposite sides of a rectangle have the same length, we can fill in some of the side lengths as shown:

Thingy

The figure is a 60-by-40 rectangle cut from a 100-by-100 square, so, to get the area of the figure, subtract the area of the former from that of the latter. The area of a rectangle is equal to the product of its dimensions, so the areas of the rectangle and the square are, respectively,

and 

,

making the area of the figure

.

Example Question #6 : Area

A circle is inscribed in square that has a side length of , as shown by the figure below.

1

Find the area of the shaded region. Use .

Possible Answers:

Correct answer:

Explanation:

2

Since the circle is inscribed in the square, the diameter of the circle is the same length as the length of a square.

Start by finding the area of the square.

For the given square,

Now, because the diameter of the circle is the same as the length of a side of the square, we now also know that the radius of the circle must be . Next recall how to find the area of a circle.

Plug in the found radius to find the area of the circle.

Now, the shaded area is the area left over when the area of the circle is subtracted from the area of the square. Thus, we can write the following equation to find the area of the shaded region.

Example Question #8 : Area

Josh wants to build a circular pool in his square yard that measures  feet on each side. He wants to build the pool as big as possible, then pave the rest of his yard in tile. In square feet, what is the area of the yard that will be tiled? Round your answer to the nearest tenths place.

Possible Answers:

Correct answer:

Explanation:

Start by drawing out the square yard and the circular pool in a way that maximizes the area of the pool.

2

Notice that the diameter of the pool will be the same length as the side of the square. 

Since the question asks about the area that is left over after the pool is built, we can find that area by subtracting the area of the pool from the area of the square.

Start by finding the area of the square.

Next, find the area of the circular pool.

Since the diameter of the pool is , the radius of the pool must be . Recall how to find the area of a circle:

Plug in the radius of the circle.

Subtract the area of the circle from that of the square.

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