A roll of wallpaper has a diameter of 20 inches. What is the diameter of the roll of wallpaper when one-fourth of the material has been removed?

Question

pls help i have to turn this in sooon

Answer 1

Wait, circular wallpaper? Okay....

Here's what we know:

A = πr² (area of a circle)

r = d/2 ⇒ 20/2 = 10 (radius is half of the diameter)

 

A = 3.14 * 10²

A = 3.14 * 100 = 314

 

If we remove 1/4, then there's 3/4 left:

314 * 3/4 = 235.5

That's the area of smaller circle

235.5 = 3.14r²

Divide by 3.14:

75 = r²

√75 = r

double the radius to get back to diameter:

2√75 = d