Question

notes circumference is the c = 2 x 3.14 x r (r = radius) or c = 3.14 x d (d = diameter) ex #1 find the circumference of a circle with a radius of 4.5 cm. 4.5 cm c = 2 x 3.14 x 4.5 c = ____ cm ex #2 find the circumference of a circle with a diameter of 1.7 m. 1.7 m c = 3.14 x 1.7 c = ____ m practice 1. find the circumference of each circle below. show work! a) 10 cm b) 8 m

Explanation:

Step1: Recall the formula for circumference

When the diameter $d$ is given, $C = 3.14\times d$; when the radius $r$ is given, $C=2\times3.14\times r$.

Step2: Solve Ex #1

Given $r = 4.5$ cm, use $C = 2\times3.14\times r$. So $C=2\times3.14\times4.5=28.26$ cm.

Step3: Solve Ex #2

Given $d = 1.7$ m, use $C = 3.14\times d$. So $C=3.14\times1.7 = 5.338$ m.

Step4: Solve Practice a

Given $d = 10$ cm, use $C = 3.14\times d$. So $C=3.14\times10=31.4$ cm.

Step5: Solve Practice b

Given $r = 8$ m, use $C = 2\times3.14\times r$. So $C=2\times3.14\times8=50.24$ m.

Answer:

Ex #1: 28.26 cm
Ex #2: 5.338 m
Practice a: 31.4 cm
Practice b: 50.24 m