You can find diameter of a circle by multiplying the radius of a circle by two: Diameter = 2 * Radius. Lisa studied mathematics at the University of Alaska, Anchorage, and spent several years tutoring high school and university students through scary -- but fun! Question 3: If the area of a circle is 154 cm 2, then find the radius of the circle. This tutorial shows you how to use that formula and the given value for the area to find the radius. The radius is the length from the center of a … Multiply the volume of your sphere by 3/4. John cut out a circle of radius \(5 \:\text{cm}\) from … You may have to do a little preliminary mathematics to get to the radius. To calculate the area, you just need to enter a positive numeric value in one of the 3 fields of the calculator. Just plug that value into the formula for the area of a circle and solve. Just plug that value into the formula for the area of a circle and solve. Find the ratio of their circumference. You can use the area to find the radius and the radius to find the area of a circle. Just plug that value into the formula for the area of a circle and solve. Since the diameter of the circle is 6 feet, the radius must be 3 feet (the radius is always half of the diameter). View Answer. Calculates the radius, diameter and circumference of a circle given the area. or, when you know the Circumference: A = C2 / 4π. MEDIUM. Set up the formula for the area of a circle. Formula. Since π is constant, we need only the radius value from the user to calculate the area. Start by recalling that the standard formula for area of a circle is π​r​2, where ​r​ is the radius. If the diameter (d) is equal to 10, you write this value as d = 10. The result of this step represents ​r​2 or the circle's radius squared. (Circumference is just a fancy word for the perimeter of any round object). Note: If you know the radius of a circle, you can use it to find the area of that circle. So, we can apply the formula using \(r = 3\). Enter the area contained within a circle. How to Find Area of a Sector. Find out ratio of their areas. r = Circle radius; A = Circle area; π = Pi = 3.14159… Area of Circle. If the diameter of a circle is 8.8cm, then the radius turns out to be 4.4cm. Area has different units, but you can use: square mils, square inches, square feet, square yards, square miles, acres, hectares, square millimeters, square centimeters, square meters, and square kilometers. Copyright 2021 Leaf Group Ltd. / Leaf Group Media, All Rights Reserved. Then you can use the formula for the area of a circle to solve! Visual on the figure below: π is, of course, the famous mathematical constant, equal to about 3.14159, which was originally defined … You cannot find the area of a sector if you do not know the radius of the circle. So your answer is right there in front of you. Use this formula to find the radius when the problem tells you the area of the circle. To use our calculator, you only need to know the radius of your circle. The radius of a circle is the straight-line distance from the very center of the circle to any point on the circle. Distance between centers of two intersecting circles if the radii and common chord length is given. You can find the circumference by using … Solution. Imagine that you have a small sphere with volume 113.04 in3. A circle of radius = 6 or diameter = 12 or circumference = 37.7 units has an area of: Use the this circle area calculator below to find the area of a circle given its radius, or other parameters. Did you know that you can figure out the formula for the area of a circle by first turning the circle into a parallelogram? The ratio of radii of two circles is \(2:3\). A circle is the set of all points on a plane with the same distance (the radius) to a certain point, which is called center. Divide the result of Step 1 by 2 to get the circle's radius. What is the Formula for the Area of a Circle? or, when you know the Diameter: A = (π /4) × D2. Learn how to use this formula to find the area of a circle when given the diameter. Conclude your calculations by taking the cube root of the result from Step 2; the result is the radius of your sphere. You just have to isolate it using appropriate mathematical operations. Begin by dividing your area by π, usually approximated as 3.14: 50.24 ft2 ÷ 3.14 = 16 ft2 You aren't quite done yet, but you're close. \ (\pi r^2\) means \ (\pi \times r \times r\). The formula for finding a sphere's volume (​V​) is a little more complicated. -- math subjects like algebra and calculus. Given the area, A A, of a circle, its radius is the square root of the area divided by pi: r = √A π r = A π Using the Area 1. C: is the circumference of a circle. The radius is equal to half of the diameter. If you know any of these other measurements, you can work backwards from standard formulas to figure out the circle or sphere's radius. How Do You Find the Area of a Circle if You Know the Diameter. Figuring out a circle's radius based on its diameter is the easiest calculation possible: Just divide the diameter by 2, and you'll have the radius. r: is the radius of a circle. How to find the area of a circle: The area of a circle can be found by multiplying pi ( π = 3.14) by the square of the radius; If a circle has a radius of 4, its area is 3.14*4*4=50.24; If you know the diameter, the radius is 1/2 as large. A circle's radius is exactly half the length of the same circle's diameter, which is a line that divides the circle into two equal halves. The formula for working out the area of a circle is: \ (A = \pi r^2\), where \ (r\) is the radius of the circle. In this case, you have: √16 ft2 = 4 ft So the circle's radius, r, is 4 feet. If you have the diameter of a circle, you can use it to find the area of that circle. You can also modify this program to take the diameter as input from the user. Sphere surface area to radius calculator; User Guide. The result of this step represents r2 or the circle's radius squared. Just plug that value into the formula for the area of a circle and solve. ... 2. Then you can use the formula for the circumference of a circle to get the answer! Circle Calculator. The formula for the area of a circle is π x radius2, but the diameter of the circle is d = 2 x r 2, so another way to write it is π x (diameter / 2)2. You can't do algebra without working with variables, but variables can be confusing. So if you know the circumference, you can calculate the circle's radius too. Imagine that you have a very big circle of area 50.24 ft2. This tutorial shows you how! This gives you: Note how you carry the units of measure all the way through your calculations. Radius of Circle. Be careful, though; you may be able to find the radius if you have either the diameter or the circumference. π: is a constant, whose value is 3.1415 or 22/7. Divide the area by π {\displaystyle \pi }. Therefore, the radius of the circle is 7cm. The area of a circle is the space it occupies, measured in square units. If you know the radius of a circle, you can use it to find the area of that circle. You'll also see what happens when you don't follow these rules, and you'll find out why order of operations is so important! Circle Area Calculation Formula. Thus, if there were a total of 28.26 squares, the area of this circle would be 28.26 cm 2 However, it is easier to use one of the following formulas: or where is the area, and is the radius. area S. 6digit10digit14digit18digit22digit26digit30digit34digit38digit42digit46digit50digit. Then click Calculate. Just plug the value for the diameter into the formula and solve. So here is the formula: (R) 2 X π = Area of the circle. If you know the radius of a circle, you can use it to find the area of that circle. Watch this tutorial to see how it's done! 4. Begin by dividing your area by π, usually approximated as 3.14: You aren't quite done yet, but you're close. The nature of the radius makes it a powerful building block for understanding many other measurements about a circle, for example its diameter, its circumference, its area and even its volume (if you're dealing with a three-dimensional circle, also known as a sphere). So you have: Your sphere has a radius of 3 inches; that would make it something like a super-sized marble, but still small enough to hold in your palm. Trying to find the circumference of a circle? How to Calculate Radius of a Circle from Area. Note that if a unit of measurement is given, it's important to carry it all the way through your calculations. What is its radius? Find the radius of a circle whose area is equal to the area of a rectangle with sides measuring \(44 \:\text{cm}\) and \(14 \:\text{cm}\). A circle of radius = 28 or diameter = 56 or circumference = 175.9 cm has an area of: 2.463 × 10 -7 square kilometers (km²) 0.2463 square meters (m²) 2463 square centimeters (cm²) It seems a little weird, but it really works! The general relationship between radius and the diameter is that the radius is half of the diameter. The radius of any circle is always half the diameter. So if the circle has a diameter of 8 inches, you calculate the radius like this: The circle's radius is 4 inches. This tool will calculate the radius of a circle from the area, and will convert different measurement units for area and radius. The major parts of a circle that a student comes across in around 3rd or 4th grade are the Radius Of A Circle, Circumference of a Circle, Diameter of the circle, and the Area of the Circle.The three are a lot different from each other, but what connects them is the measurement of the radius of the given circle. How Do You Find the Circumference of a Circle if You Know the Diameter?