All ISEE Upper Level Math Resources
Example Questions
Example Question #103 : Geometry
What is the area of a circle with a diameter equal to 6?
First, solve for radius:
Then, solve for area:
Example Question #104 : Geometry
The diameter of a circle is . Give the area of the circle.
The area of a circle can be calculated using the formula:
,
where is the diameter of the circle, and is approximately .
Example Question #4 : Know And Use The Formulas For The Area And Circumference Of A Circle: Ccss.Math.Content.7.G.B.4
The diameter of a circle is . Give the area of the circle in terms of .
The area of a circle can be calculated using the formula:
,
where is the diameter of the circle and is approximately .
Example Question #1 : Area Of A Circle
The radius of a circle is . Give the area of the circle.
The area of a circle can be calculated as , where is the radius of the circle, and is approximately .
Example Question #3 : How To Find The Area Of A Circle
The perpendicular distance from the chord to the center of a circle is , and the chord length is . Give the area of the circle in terms of .
Chord length = , where is the radius of the circle and is the perpendicular distance from the chord to the circle center.
Chord length =
, where is the radius of the circle and is approximately .
Example Question #1 : Area Of A Circle
The circumference of a circle is inches. Find the area of the circle.
Let .
First we need to find the radius of the circle. The circumference of a circle is , where is the radius of the circle.
The area of a circle is where is the radius of the circle.
Example Question #2 : How To Find The Area Of A Circle
In the above figure, .
What percent of the figure is shaded gray?
For the sake of simplicity, we will assume that ; this reasoning is independent of the actual length.
The four concentric circles have radii 1, 2, 3, and 4, respectively, and their areas can be found by substituting each radius for in the formula :
The outer gray ring is the region between the largest and second-largest circles, and has area
The inner gray ring is the region between the second-smallest and smallest circles, and has area
The total area of the gray regions is
Since out of total area is gray, the percent of the figure that is gray is
.
Example Question #43 : Circles
In the above figure, .
Give the ratio of the area of the outer ring to that of the inner circle.
12 to 1
9 to 1
16 to 1
7 to 1
7 to 1
For the sake of simplicity, we will assume that ; this reasoning is independent of the actual length.
The four concentric circles have radii 1, 2, 3, and 4, respectively, and their areas can be found by substituting each radius for in the formula .
The areas of the largest circle and the second-largest circle are, respectively,
The difference of their areas, which is the area of the outer ring, is
.
The inner circle has area
.
The ratio of these areas is therefore
, or 7 to 1.
Example Question #3 : How To Find The Area Of A Circle
The above figure depicts a dartboard, in which .
A blindfolded man throws a dart at the target. Disregarding any skill factor and assuming he hits the target, what are the odds against his hitting the white inner circle?
16 to 1
8 to 1
15 to 1
7 to 1
15 to 1
For the sake of simplicity, we will assume that ; this reasoning is independent of the actual length.
The inner and outer circles have radii 1 and 4, respectively, and their areas can be found by substituting each radius for in the formula :
- this is the white inner circle.
The area of the portion of the target outside the white inner circle is , so the odds against hitting the inner circle are
- that is, 15 to 1 odds against.
Example Question #941 : Grade 7
What is the area of a circle with a diameter of , rounded to the nearest whole number?
The formula for the area of a circle is
Find the radius by dividing 9 by 2:
So the formula for area would now be: