All High School Math Resources
Example Questions
Example Question #211 : High School Math
A square has an area of 32 in2. If a circle is inscribed within the square, what is its area?
4√2 in2
2√2 in2
16π in2
8π in2
32π in2
8π in2
The diameter of the circle is the length of a side of the square. Therefore, first solve for the length of the square's sides. The area of the square is:
A = s2 or 32 = s2. Taking the square root of both sides, we get: s = √32 = √(25) = 4√2.
Now, based on this, we know that 2r = 4√2 or r = 2√2. The area of the circle is πr2 or π(2√2)2 = 4 * 2π = 8π.
Example Question #212 : High School Math
A manufacturer makes wooden circles out of square blocks of wood. If the wood costs $0.25 per square inch, what is the minimum waste cost possible for cutting a circle with a radius of 44 in.?
1936π dollars
7744 – 1936π dollars
5808 dollars
1936 – 484π dollars
1936 dollars
1936 – 484π dollars
The smallest block from which a circle could be made would be a square that perfectly matches the diameter of the given circle. (This is presuming we have perfectly calibrated equipment.) Such a square would have dimensions equal to the diameter of the circle, meaning it would have sides of 88 inches for our problem. Its total area would be 88 * 88 or 7744 in2.
Now, the waste amount would be the "corners" remaining after the circle was cut. The area of the circle is πr2 or π * 442 = 1936π in2. Therefore, the area remaining would be 7744 – 1936π. The cost of the waste would be 0.25 * (7744 – 1936π). This is not an option for our answers, so let us simplify a bit. We can factor out a common 4 from our subtraction. This would give us: 0.25 * 4 * (1936 – 484π). Since 0.25 is equal to 1/4, 0.25 * 4 = 1. Therefore, our final answer is: 1936 – 484π dollars.
Example Question #21 : How To Find The Area Of A Circle
A manufacturer makes wooden circles out of square blocks of wood. If the wood costs $0.20 per square inch, what is the minimum waste cost possible for cutting a circle with a radius of 25 in.?
2500 - 625π dollars
500 dollars
500 - 125π dollars
625 - 25π dollars
625 dollars
500 - 125π dollars
The smallest block from which a circle could be made would be a square that perfectly matches the diameter of the given circle. (This is presuming we have perfectly calibrated equipment.) Such a square would have dimensions equal to the diameter of the circle, meaning it would have sides of 50 inches for our problem. Its total area would be 50 * 50 or 2500 in2.
Now, the waste amount would be the "corners" remaining after the circle was cut. The area of the circle is πr2 or π * 252 = 625π in2. Therefore, the area remaining would be 2500 - 625π. The cost of the waste would be 0.2 * (2500 – 625π). This is not an option for our answers, so let us simplify a bit. We can factor out a common 5 from our subtraction. This would give us: 0.2 * 5 * (500 – 125π). Since 0.2 is equal to 1/5, 0.2 * 625 = 125. Therefore, our final answer is: 500 – 125π dollars.
Example Question #213 : High School Math
25π
100π
50π
10π
20π
50π
Example Question #214 : High School Math
A circle with diameter of length is inscribed in a square. Which of the following is equivalent to the area inside of the square, but outside of the circle?
In order to find the area that is inside the square but outside the circle, we will need to subtract the area of the circle from the area of the square. The area of a circle is equal to . However, since we are given the length of the diameter, we will need to solve for the radius in terms of the diameter. Because the diameter of a circle is twice the length of its radius, we can write the following equation and solve for :
Divide both sides by 2.
We will now substitute this into the formula for the area of the circle.
area of circle =
We next will need to find the area of the square. Because the circle is inscribed in the square, the diameter of the circle is equal to the length of the circle's side. In other words, the square has side lengths equal to d. The area of any square is equal to the square of its side length. Therefore, the area of the square is .
area of square =
Lastly, we will subtract the area of the circle from the area of the square.
difference in areas =
We will rewrite so that its denominator is 4.
difference in areas =
The answer is .
Example Question #314 : Sat Mathematics
An original circle has an area of . If the radius is increased by a factor of 3, what is the ratio of the new area to the old area?
The formula for the area of a circle is . If we increase by a factor of 3, we will increase the area by a factor of 9.
Example Question #31 : Radius
A square has an area of . If the side of the the square is the same as the diameter of a circle, what is the area of the circle?
The area of a square is given by so we know that the side of the square is 6 in. If a circle has a diameter of 6 in, then the radius is 3 in. So the area of the circle is or .
Example Question #215 : High School Math
Mary has a decorative plate with a diameter of ten inches. She places the plate on a rectangular placemat with a length of 18 inches and a width of 12 inches. How much of the placemat is visible?
First we will calculate the total area of the placemat:
Next we will calculate the area of the circular place
And
So
We will subtract the area of the plate from the total area
Example Question #24 : How To Find The Area Of A Circle
The picture above contains both a circle with diameter 4, and a rectangle with length 8 and width 5. Find the area of the shaded region. Round your answer to the nearest integer
First, recall that the diameter of a circle is twice the value of the radius. Therefore a circle with diameter 4 has a radius of 2. Next recall that the area of a circle with radius is:
The area of the rectangle is the length times the width:
The area of the shaded region is the difference between the 2 areas:
The nearest integer is 27.
Example Question #216 : High School Math
Allen was running around the park when he lost his keys. He was running around aimlessly for the past 30 minutes. When he checked 10 minutes ago, he still had his keys. Allen guesses that he has been running at about 3m/s.
If Allen can check 1 square kilometer per hour, what is the longest it will take him to find his keys?
Allen has been running for 10 minutes since he lost his keys at 3m/s. This gives us a maximum distance of from his current location. If we move 1800m in all directions, this gives us a circle with radius of 1800m. The area of this circle is
Our answer, however, is asked for in kilometers. 1800m=1.8km, so our actual area will be square kilometers. Since he can search 1 per hour, it will take him at most 10.2 hours to find his keys.
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