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Example Questions
Example Question #33 : Quadrilaterals
Quantity A
The perimeter of a square with a diagonal of 12 inches.
Quantity B
The perimeter of a rectangle with a diagonal of 10 inches and longer sides that are three times the length of its shorter sides.
The relationship cannot be determined from the information given.
The quantities are equal.
Quantity A is greater.
Quantity B is greater.
Quantity A is greater.
The diagonal of a square creates a 45-45-90 triangle; therefore, considering x as the value for the sides of the square in A, set up the ratio: 1/√2 = x/12 → x = 12/√2
Simplify the square root out of the denominator: x = (12√2)/2 = 6√2. The perimeter is equal to 4x; therefore, quantity A is 24√2.
Use the Pythagorean Theorem for B. We know that one side of the triangle is x and the other must be 3x. Furthermore, we know the hypotenuse is 10; therefore:
x2 + (3x)2 = 102 → x2 + 9x2 = 100 → 10x2 = 100 → x2 = 10 → x = √10.
Transform the √10 into √2 * √5 ; therefore, x = √2 * √5 . The perimeter of the rectangle will equal 3x + 3x + x + x = 8x = 8√2 * √5 .
Compare these two values. Quantity A has a coefficient of 24 in for its √2 . Quantity B has a coefficient of 8√5, which must be smaller than 24, because 8 * 3 = 24, but √5 is less than 3 (which would be √9 ); therefore, A is larger.
Example Question #1 : How To Find The Perimeter Of A Rectangle
A rectangle has a length that is twice that of its height. If the perimeter of that rectangle is , what is its area?
Based on our first sentence, we know:
The second sentence means:
, which is the same as:
Now, we can replace with
in the second equation:
Therefore,
Now, this means that:
If these are our values, then the area of the rectangle is:
Example Question #163 : Geometry
A rectangle with an area of 64 square units is one-fourth as wide as it is long. What is the perimeter of the rectangle?
Begin by setting up a ratio of width to length for the rectangle. We know that the width is one-fourth the length, therefore
.
Now, we can substitute W in the rectangle area formula with our new variable to solve for the length.
Solve for length:
Using the length, solve for Width:
Now, plug the length and width into the formula for the perimeter of a rectangle to solve:
The perimeter of the rectangle is 40.
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