Question

lesson 14

1. rounded to the nearest whole number, what is the circumference of this circle? 6.2 mi

12 mi.
39 mi.
eyes color: green
eyes color: blue

1. find the area of the shaded part. 16

36
1218.32 ft²
816.4 ft²
mouth color: green
mouth color: red
find the area of the giant
1,962.5 in²
7,850 in²
limbs color: purple
limbs color: pink

1. in which case would it be necessary to find the area of this circle?

to cover the surface of the dartboard
to make a frame around the dartboard
sleeves color: yellow
sleeves color: red

1. the diameter of a circle is 100cm. what is the area of the circle?

a = 7,850 cm²
a = 31,400 cm²
floor color: green
floor color: black

1. a circular pool cover has a radius of four feet. which represents the area of the pool cover?

8π in²
16π in²
boots color: gray
boots color: orange

1. the area of a circle is 153.9cm². which is the approximate size of its radius?

about 14 cm
about 7 cm
shell color: blue
shell color: brown

1. the radius of the slice is 5cm. the slice gets dipped in ink and used as a stamp. what area does the stamp cover?

a = 7.85 cm²
a = 78.5 cm²
nose color: purple
nose color: green

Explanation:

11.

Step1: Recall the circumference formula

The formula for the circumference of a circle is $C = 2\pi r$ or $C=\pi d$, where $r$ is the radius and $d$ is the diameter. Given $r = 6.2$ mi, we use $C = 2\pi r$.

Step2: Calculate the circumference

$C=2\times\pi\times6.2\approx2\times3.14\times6.2 = 38.936$ mi.

Step3: Round to the nearest whole number

Rounding $38.936$ to the nearest whole - number gives $39$ mi.

Step1: Recall the area formula for a circle

The formula for the area of a circle is $A=\pi r^{2}$. Given $r = 5$ cm, we substitute $r$ into the formula.

Step2: Calculate the area

$A=\pi\times(5)^{2}=25\pi\approx25\times3.14 = 78.5$ $cm^{2}$

Step1: Find the area of the outer circle

The radius of the outer circle $R = 36\div2=18$ ft. The area of the outer circle $A_{1}=\pi R^{2}=\pi\times(18)^{2}=324\pi$ $ft^{2}$.

Step2: Find the area of the inner circle

The radius of the inner circle $r = 16\div2 = 8$ ft. The area of the inner circle $A_{2}=\pi r^{2}=\pi\times(8)^{2}=64\pi$ $ft^{2}$.

Step3: Calculate the area of the shaded part

The area of the shaded part $A = A_{1}-A_{2}=\pi(324 - 64)=260\pi\approx260\times3.14=816.4$ $ft^{2}$

Answer:

$39$ mi

12.