radius | MathCelebrity Forum

radius

  1. math_celebrity

    When the circumference of a circle is increased from 10 pi inches to 15 pi inches, by how many inche

    When the circumference of a circle is increased from 10 pi inches to 15 pi inches, by how many inches is the radius increased? C = 2pir Smaller circle: 2pir = 10pi Divide each side by 2pi: r = 5 Larger circle: 2pir = 15pi Divide each side by 2pi: r = 7.5 Difference = 7.5 - 5 = 2.5 or 2&1/2
  2. math_celebrity

    Three tennis balls each have a radius of 2 inches. They are put into a 12 inch high cylinder with a

    Three tennis balls each have a radius of 2 inches. They are put into a 12 inch high cylinder with a 4 inch diameter. What is the volume of the space remaining in the cylinder? Volume of each ball is 4/3 πr^3 V = 4/3 * 3.1415 * 2^3 V = 1.33 * 3.1415 * 8 = 33.41 cubic inches The volume of 3...
  3. math_celebrity

    When a circle's radius triples, what happens to its area?

    When a circle's radius triples, what happens to its area? A = πr^2 When r = 3r, then we have: a = π(3r)^2 A = 9(πr^2) This means Area increases by 9x
  4. math_celebrity

    What is the formula for the volume of a cylinder?

    What is the formula for the volume of a cylinder? The Volume (V) of a cylinder with radius (r) and height (h) is: V = πr^2h
  5. math_celebrity

    Fantasia decided to paint her circular room which had a diameter of 25 feet. She started painting in

    Fantasia decided to paint her circular room which had a diameter of 25 feet. She started painting in the center and when she had painted a circle with a 5-foot diameter, she used one quart of paint. How many more quarts of paint must Fantasia buy to finish her room? The area formula for a...
  6. math_celebrity

    The button on Alice's shirt has a diameter of 8 millimeters. What is the button's radius?

    The button on Alice's shirt has a diameter of 8 millimeters. What is the button's radius? Radius = Diameter / 2 Radius = 8/2 Radius = 4
  7. math_celebrity

    if my diameter is 19 inches, what is my radius?

    if my diameter is 19 inches, what is my radius? Radius = Diameter/2 Radius = 19/2
  8. math_celebrity

    A penny has a diameter of 19 millimeters. What is the radius of the penny.

    A penny has a diameter of 19 millimeters. What is the radius of the penny. D = 2r To solve for r, we divide each side by 2: r = D/2 Plugging in D = 19, we get: r = 19/2 or 9.5
  9. math_celebrity

    A circular balloon is inflated with air flowing at a rate of 10cm3/s. How fast is the radius of the

    A circular balloon is inflated with air flowing at a rate of 10cm3/s. How fast is the radius of the ballon increasing when the radius is 2cm? The volume (V) of the balloon with radius (r) is: V = 4/3πr^3 Differentiating with respect to t, we get: dV/dt = 4/3π * 3r^2 * dr/dt dV/dt = 4πr^2 *...
Back
Top