How do I do this (Math)

Easy. Say your weight measures 2" thick x 12" wide at the bottom where you want to cut to be.
Weight of steel .28lbs/ci

2 x 12 = 24ci
24 x .28= 6.72lbs for every 1" of material at the bottom or 1"x 2"x 12" existing

18/6.72= 2.68" to cut off or the drop off piece would be 2.68"x 2"x 12".

math check:
2.68x 2 x 12= 64.32ci x .28lb/ci = 18lbs - 68lbs = 50lbs

Only if you wanted to make a equal cut all the way around would your 65.125" measurement be needed, so it's confusing you, get rid of it.

T_Bone

Ok now I should cut off 68 sq in to get to the 50 lbs I want. But because this weight has angles on it is not that simple to figure how to get the 68 sq in. What I need to know is at 68 sq in how long would my string be so I can lay it out on the weight? I hope that makes some sense
BUDD

BUDD

I would put the weight in a container and have the weight attached to a string.
I would mark how high the water level is with the weight submerged.
I would pull the weight out.
I would carefully fill the container back up with water which is measured by liters or gallons or what ever you are use to.
From that you can find how much it weighs per unit (which ever you chose)
For instance, I would use liters being I am a metric person.
I would find exactly how many liters and milliliters it took to fill the container to its original height with the weight in it.
From that I would multiply by 61 to get cubic inches.
That will be how big the weight is in cid.

Now take the weight (68lbs) divided by the cubic inches.
That will tell you how much each cubic inch weights.
With that knowledge you can figure out how much to cut off the square end.

I would still cut twice. Leave some for error.

You start with:

Mass = volume*density,

so, Volume = Mass/Density.

Your mass is 18lb, so your volume is:

18lbs/density

Now you know the volume you can work out from

Volume = length*width*thickness

to find the unknown (you measure the thickness and the length (from front to back)) you rearrange to find width, so:

Volume/(length*thickness) = width

Now you know from the first equation that the Volume is 18/density, so

(18/density)/(length*thickness) = width

Easy when you do it in simple stages, but make sure all your units are the same (don"t mix feet with inches or metres or anything else)

Regards, RAB

10 cubic inches= 2.9#

62 cubic inches = 18#

Even bad boys are just as good as they can be