The Parts of a Circle: Calculate the ratio between radii of two circles

Examples with solutions for The Parts of a Circle: Calculate the ratio between radii of two circles

Exercise #1

How many times longer is the radius of the red circle than the radius of the blue circle?

168

Video Solution

Step-by-Step Solution

To solve this problem, we will calculate the ratio of the radius of the red circle to the radius of the blue circle.

Here are the steps:

  • Step 1: Identify the radii of the circles:
    Radius of the red circle is half of the diameter, rred=8 r_{\text{red}}=8
    Radius of the blue circleis half of the diameter, rblue=4 r_{\text{blue}}=4

  • Step 2: Use the formula for the ratio:
    Ratio=rredrblue=84 \text{Ratio}=\frac{r_{\text{red}}}{r_{\text{blue}}}=\frac{8}{4}

  • Step 3: Simplify the ratio:
    168=2 \frac{16}{8} = 2

Therefore, the radius of the red circle is twice the radius of the blue circle.

Therefore, the solution to the problem is 2 2 .

Answer

2 2

Exercise #2

How many times longer is the radius of the red circle, which has a diameter of 24, than the radius of the blue circle, which has a diameter of 12?

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

  • Step 1: Calculate the radius of the red circle.
  • Step 2: Calculate the radius of the blue circle.
  • Step 3: Determine the ratio of the radius of the red circle to that of the blue circle.
  • Step 4: Simplify the ratio to find how many times longer the red radius is than the blue radius.

Now, let’s proceed:

Step 1: The radius of the red circle is calculated as follows:

Radius of red circle=Diameter of red circle2=242=12 \text{Radius of red circle} = \frac{\text{Diameter of red circle}}{2} = \frac{24}{2} = 12

Step 2: Similarly, the radius of the blue circle is calculated as:

Radius of blue circle=Diameter of blue circle2=122=6 \text{Radius of blue circle} = \frac{\text{Diameter of blue circle}}{2} = \frac{12}{2} = 6

Step 3: Determine the ratio of the red circle’s radius to the blue circle’s radius:

Ratio=Radius of red circleRadius of blue circle=126 \text{Ratio} = \frac{\text{Radius of red circle}}{\text{Radius of blue circle}} = \frac{12}{6}

Step 4: Simplify this ratio:

126=2 \frac{12}{6} = 2

Thus, the radius of the red circle is 2 times longer than the radius of the blue circle.

Answer

2

Exercise #3

How many times longer is the radius of the red circle (14 cm) than the radius of the blue circle, which has a diameter of 7?

Video Solution

Step-by-Step Solution

To solve this problem, let's follow these steps:

  • Step 1: Calculate the radius of the blue circle from its diameter.
  • Step 2: Determine the ratio of the radius of the red circle to the radius of the blue circle.

Now, let's carry out each step:

Step 1: The diameter of the blue circle is 7 cm. The radius, therefore, is half of the diameter:
Radius of the blue circle=72=3.5 cm \text{Radius of the blue circle} = \frac{7}{2} = 3.5 \text{ cm}

Step 2: We now find out how many times longer the radius of the red circle (14 cm) is than the radius of the blue circle:
Ratio=Radius of the red circleRadius of the blue circle=143.5=4 \text{Ratio} = \frac{\text{Radius of the red circle}}{\text{Radius of the blue circle}} = \frac{14}{3.5} = 4

Therefore, the radius of the red circle is 4 times longer than the radius of the blue circle.

Answer

4

Exercise #4

How many times longer is the radius of the red circle than the radius of the blue circle?

220

Video Solution

Answer

5

Exercise #5

How many times longer is the radius of the red circle than the radius of the blue circle?

210

Video Solution

Answer

212 2\frac{1}{2}