All ISEE Upper Level Math Resources
Example Question #1 : How To Find The Area Of A Square
A square is made into a rectangle by increasing the width by 20% and decreasing the length by 20%. By what percentage has the area of the square changed?
the area remains the same
increased by 20%
decreased by 10%
decreased by 4%
decreased by 4%
The area decreases by 20% of 20%, which is 4%.
The easiest way to see this is to plug in numbers for the sides of the square. If we are using percentages, it is easiest to use factors of 10 or 100. In this case we will say that the square has a side length of 10.
10% of 10 is 1, so 20% is 2. Now we can just increase one of the sides by 2, and decrease another side by 2. So our rectangle has dimensions of 12 x 8 instead of 10 x 10.
The original square had an area of 100, and the new rectangle has an area of 96. So the rectangle is 4 square units smaller, which is 4% smaller than the original square.
Example Question #2 : How To Find The Area Of A Square
Side shown in the diagram of square below is equal to 21cm. What is the area of ?
Cannot be determined
To find the area of a quadrilateral, multiply length times width. In a square, since all sides are equal, is both the length and width.
Example Question #3 : How To Find The Area Of A Square
If Amy is carpeting her living room, which meaures feet by feet, how many square feet of carpet will she need?
To find the area of the floor, multiply the length of the room by the width (which is the same forumla used to find the area of a square). The equation can be written:
Substitute feet for and feet for :
Amy will need of carpet.
Example Question #4 : How To Find The Area Of A Square
A rectangle and a square have the same perimeter. The rectangle has length centimeters and width centimeters. Give the area of the square.
The perimeter of the rectangle is
This is also the perimeter of the square, so divide this by to get its sidelength:
The area is the square of this, or square centimeters.
Example Question #5 : How To Find The Area Of A Square
Four squares have sidelengths 4 inches, 8 inches, 12 inches, and 16 inches. What is the average of their areas?
The areas of the four squares can be calculated by squaring their sidelengths. Add these areas, then divide by 4:
Example Question #6 : How To Find The Area Of A Square
Which of the following is equal to the area of a square with sidelength yards?
Multiply the sidelength by 36 to convert from yards to inches:
Square this to get the area:
Example Question #7 : How To Find The Area Of A Square
What is the area of a square in which the length of one side is equal to ?
The area of a square is equal to the product of one side multiplied by another side. Therefore, the area will be equal to:
The next step is to convert the fractions being added together to a form in which they have a common denominator. This gives us:
Example Question #8 : How To Find The Area Of A Square
One of the sides of a square on the coordinate plane has its endpoints at the points with coordinates and . What is the area of this square?
The length of a segment with endpoints and can be found using the distance formula with , , , :
This is the length of one side of the square, so the area is the square of this, or 122.
Example Question #9 : How To Find The Area Of A Square
One of the sides of a square on the coordinate plane has its endpoint at the points with coordinates and , where and are both positive. Give the area of the square in terms of and .
The length of a segment with endpoints and can be found using the distance formula as follows:
This is the length of one side of the square, so the area is the square of this, or .
Example Question #10 : How To Find The Area Of A Square
One of the vertices of a square is at the origin. The square has area 13. Which of the following could be the vertex of the square opposite that at the origin?
Since a square is a rhombus, one way to calculate the area of a square is to take half the square of the length of a diagonal. If we let be the length of each diagonal, then
Therefore, we want to choose the point that is units from the origin. Using the distance formula, we see that is such a point:
Of the other points: