Rectangles
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Math › Rectangles
A rectangle has an area of . The width is four less than the length. What is the perimeter?
Explanation
For a rectangle, area is and perimeter is
, where
is the length and
is the width.
Let = length and
= width.
The area equation to solve becomes , or
.
To factor, find two numbers the sum to -4 and multiply to -96. -12 and 8 will work:
x2 + 8x - 12x - 96 = 0
x(x + 8) - 12(x + 8) = 0
(x - 12)(x + 8) = 0
Set each factor equal to zero and solve:
or
.
Therefore the length is and the width is
, giving a perimeter of
.

Note: Figure NOT drawn to scale
The above figure shows Rhombus .
Which is the greater quantity?
(a)
(b)
(a) and (b) are equal
It is impossible to determine which is greater from the information given
(b) is the greater quantity
(a) is the greater quantity
Explanation
The opposite sides of a parallelogram - a rhombus included - are congruent, so
.
Also, Quadrilateral form a rectangle; since
and
, it follows that
, and, similarly,
. Therefore,
, and
Find the area of a rectangle with a length of 16cm and a width that is a quarter of the length.
Explanation
To find the area of a rectangle, we will use the following formula:
where l is the length and w is the width of the rectangle.
Now, we know the length of the rectangle is 16cm. We also know the width of the rectangle is a quarter of the length. To find the width, we will divide 16 by 4. Therefore, the width the 4cm.
Knowing this, we will substitute into the formula. We get
Find the area of a rectangle with a length of 12cm and a width that is a quarter of the length.
Explanation
To find the area of a rectangle, we will use the following formula:
where l is the length and w is the width of the rectangle.
Now, we know the length of the rectangle is 12cm. We also know the width of the rectangle is a quarter of the length. To find the width, we will divide 12 by 4. Therefore, the width the 3cm.
Knowing this, we will substitute into the formula. We get
Find the area of a rectangle with a length of 14in and a width that is half the length.
Explanation
To find the area of a rectangle, we will use the following formula:
where l is the length and w is the width of the rectangle.
Now, we know the length of the rectangle is 14in. We also know the width of the rectangle is half the length. Therefore, the width is 7in.
Knowing this, we will substitute into the formula. We get

Give the area of the above rectangle in square feet.
Explanation
Since 1 yard = 3 feet, multiply each dimension by 3 to convert from yards to feet:
Use the area formula, substituting :
square feet
The sum of the lengths of three sides of a rectangle is 572 inches; the width of the rectangle is 60% of its length. Give its area in square inches.
It is impossible to determine the area from the given information.
Explanation
Since the width of the rectangle is 60% of its length, we can write .
However, it is not clear from the problem which three sides - two lengths and a width or two widths and a length - we are choosing to have sum 572 inches. Depending on the three sides chosen, we can either set up
or
Since the length cannot be determined with certainty, neither can the width, and, subsequently, neither can the area.
A rectangular postage stamp has a width of 3 cm and a height of 12 cm. Find the area of the stamp.
Explanation
A rectangular postage stamp has a width of 3 cm and a height of 12 cm. Find the area of the stamp.
To find the area of a rectangle, we must perform the following:
Where l and w are our length and width.
This means we need to multiply the given measurements. Be sure to use the right units!
And we have our answer. It must be centimeters squared, because we are dealing with area.
A rectangle is two feet shorter than twice its width; its perimeter is six yards. Give its area in square inches.
Explanation
The length of the rectangle is two feet, or 24 inches, shorter than twice the width, so, if is the width in inches, the length in inches is
Six yards, the perimeter of the rectangle, is equal to inches. The perimeter, in terms of length and width, is
, so we can set up the equation:
The length and width are 64 inches and 44 inches; the area is their product, which is
square inches
The ratio of the perimeter of one square to that of another square is . What is the ratio of the area of the first square to that of the second square?
Explanation
For the sake of simplicity, we will assume that the second square has sidelength 1; Then its perimeter is , and its area is
.
The perimeter of the first square is , and its sidelength is
. The area of this square is therefore
.
The ratio of the areas is therefore .