how do you work out the radius of a circle?

Question

hi, im stuck on homework where i have:
drinking glasses with the diameter of 6cm
depth of 12cm
with internal measurments of 28.5cm long, 19cm wide and 13cm high.
the spaces inbetween the glasses is filled up with polystyrene granules.
and i have to find the volume the polystyrene granules have to fill.
i think you have to work out the radius, but its been a long time since we were taught how.
thanks

Answer 1

the radius is half the diameter.

Answer 2

Radius is one-half of the diameter, so the radius is 3 cm.

If you didn't know the diameter, you could find it by first finding the centre. Take a compass (the drawing kind) and open it so the legs are wider than half the circle. Make two arcs, one each from the left and right side of the top of the circle and two more on the left and right side of the bottom of the circle, so the arcs intersect on the top and bottom. Draw a straight line through the intersections. Then do the same thing on the top and bottom of the right side and the top and bottom of the left side. Draw a line through the intersections. Where your two straight lines cross in the middle should be dead centre. Measuring through the centre to each side will give you the diameter and the radius as well.

The formula for the volume of a cylinder is V=piR squared X h, where h=distance between the cylinder faces (the height of the cylinder).

I would work it out for you but I don't know what the difference is between your 'long' and 'high' measurements.

Good luck!

Answer 3

radius of a circle is half the diameter,

If the glasses are in a box and the polystyrene granules are filling up the spaces between the glasses, work out the volume of the box (length x width x height) then work out the volume of a glass (pi x radius squared x height), multiply the volume of the glass by the number of glasses, take the total away from the volume of the box.

Answer 4

hang on
answer in a sec.
Ok the radius is half of the diameter, so 3cm.
For the volume that the polystyrene has to fill, you can look at it by saying the base of each glass has to be fitted exactly inside a square, and the area not covered by the glass has to be filled with polystyrene. So the square will be 6cm x 6cm. The area the polystyrene has to fill is just (area of square) - (area of base of glass).
The area of the base of the glass is pi * radius^2 = 9pi.
So the area the polystyrene has to cover is 36 - 9pi.
To find the volume, you multiply (36-9pi) by the height, which is 12cm.
So the volume of polystyrene for each glass is 12*(36-9pi) = 92.7cm^3.

Answer 5

you are given that the diameter of the
glasses are 6 cm,so the radius is
3cm
you are also given the dimensions
of the container that holds the glasses
so you can work out the number of
glasses that fit into the space-remember
the depth of the glasses is 12 cm-
giving you an inch to play with

work out the volume of the container,
{L*B*H of container}
work out the number of glasses the
container holds
work out the volume of each glass
{pi*3^2*12}
(assume glasses are cylinders)
multiply the number of glasses by
the volume of each glass and
obtain VG say
then subtract VG from the volume
of the container
hey presto! roberts your father's
brother and you have the volume
of the granules!

i'm not telling you the answer
-that's your homework

i hope that this helps

Answer 6

I'm a bit unclear what the problem is. Is one glass placed inside another? If they are the volume that you want is the volume of the larger glass minus the volume of the smaller glass.
The volume of a cylinder (glass) is pi*r(squared)*h
r= radius
h=height
r=d/2 where d is the diameter.

The rest is easy peasy...

Answer 7

The radius is half of the diameter.
As you have the diameter of 6cm then the radius is 3cm.

Answer 8

the Radius is the half of Diameter,if i am right
Pi = 3.14
If you would do Diameter x Pi= ....... x high = ....... !
as i mean
6 x 3.14 = 18.84 x 12 = 226.08
diameter could be Durchmesser?
deph could be high?
I am right?

Answer 9

measure across the circle and half it