Question

A circle that originally had a circumference of 31.4 cm, now has a circumference of 15.7 cm. What happened to the radius? It was doubled. It was divided by two. It was quadrupled. It was divided by four.

Answer 1

radius was divided by 2

Explanation:

A circle that originally had a circumference of 31.4 cm, now has a circumference of 15.7 cm

Circumference of a circle formula =
`2\pi r`

where 'r' is the radius of a circle

circumference of 31.4 cm

31.4 =
`2\pi r`

the value of pi is 3.14

31.4 =
`2*3.14 r`

divide both sides by 3.14 *2

r=5

circumference of 15.7 cm.

15.7 =
`2\pi r`

the value of pi is 3.14

15.7 =
`2*3.14 r`

divide both sides by 3.14

`r=2.5`

Originally the radius = 5 cm and now the radius is 2.5 cm

It was divided by 2

Answer 2

The radius was divided by 2.

31.4 = 2pi * r

31.4/2pi = 15.7/pi

15.7 = 2pi * r

15.7/2pi = 7.85/pi

(7.85/pi) / (15.7/pi) = 1/2