All GMAT Math Resources
Example Questions
Example Question #91 : Quadrilaterals
Give the area of the above parallelogram if .
Multiply height by base to get the area.
By the 30-60-90 Theorem:
.
The area is therefore
Example Question #11 : Calculating The Area Of A Quadrilateral
Note: Figure NOT drawn to scale.
Refer to the above diagram. Give the area of Quadrilateral .
The correct answer is not among the other choices.
Apply the Pythagorean Theorem twice here.
The quadrilateral is a composite of two right triangles, each of whose area is half the product of its legs:
Area of :
Area of :
Add:
Example Question #11 : How To Find The Area Of A Rhombus
The above figure shows a rhombus . Give its area.
Construct the other diagonal of the rhombus, which, along with the first one, form a pair of mutual perpendicular bisectors.
By the Pythagorean Theorem,
The rhombus can be seen as the composite of four congruent right triangles, each with legs 10 and , so the area of the rhombus is
.
Example Question #201 : Geometry
Rhombus has perimeter 48; . What is the area of Rhombus ?
Each side of a rhombus is congruent, so if it has perimeter 48, it has sidelength 12. Also, the diagonals of a rhombus are each other's perpendicular bisectors, so if they are both constructed, and their point of intersection is called , then . The following figure is formed by the rhombus and its diagonals.
is a right triangle with its short leg half the length of its hypotenuse, so it is a 30-60-90 triangle, and its long leg measures by the 30-60-90 Theorem. Therefore, . The area of a rhombus is half the product of the lengths of its diagonals:
Example Question #14 : Other Quadrilaterals
Note: figure NOT drawn to scale.
Give the area of the above trapezoid.
The area of a trapezoid with height and bases of length and is
.
Setting :
Example Question #15 : Other Quadrilaterals
Note: figure NOT drawn to scale.
Give the area of the above trapezoid.
The area of a trapezoid with height and bases of length and is
.
Setting :
Example Question #16 : Other Quadrilaterals
Note: figure NOT drawn to scale.
The above figure depicts a rhombus, .
Give the area of Rhombus .
The area of a rhombus is half the product of the lengths of its diagonals, so
Example Question #1 : Calculating The Length Of The Diagonal Of A Quadrilateral
While walking with some friends on campus, you come across an open grassy rectangular area. You shout "Pythagoras!" and run across the rectangular area from one corner to another. If the rectangle measures meters by meters, what distance did you cover?
This problem can be solved in a variety of ways, however you do it, it may be worth eliminating any options shorter than either side of the quad. The diagonal distance is the hypotenuse of a triangle, so it must be longer than 25 or 60 meters.
Then, we can either find our hypotenuse via Pythagorean Theorem, or our knowledge of Pythagorean Triples.
Using Pythagorean Theorem:
So 65 meters.
Alternatively, recognize the triangle as a 5x/12x/13x triangle
so
Example Question #11 : Other Quadrilaterals
Given the area of a square is , what is the diagonal?
Write the formula for finding the area of a square given the diagonal.
Rearrange the equation so that the diagonal term is isolated.
Substitute the known area and simplify.
Example Question #1 : Calculating The Length Of The Diagonal Of A Quadrilateral
What is the length of the diagonal for a square with a side length of ?
The diagonal of a square is simply the hypotenuse of a right triangle whose other two sides are the length and width of the square. Because all sides of a square are equal in length, this means the length and width are both , which gives us a right triangle with a base of and a height of , for which the hypotenuse is the diagonal of the square. Applying the Pythagorean Theorem to find the length of the diagonal, we have:
So the length of the diagonal for a square with a side length of is . In general, we could check the length of the diagonal for any square with side length , and we would see that the diagonal length is always .