SOLUTION: Ran across this:
"The weight of a fraction of a square foot of any material can be quickly computed by the breakdown method;
The weight of 1 sq. ft. of steel, 0.22 in. thick
Algebra.Com
Question 1210257: Ran across this:
"The weight of a fraction of a square foot of any material can be quickly computed by the breakdown method;
The weight of 1 sq. ft. of steel, 0.22 in. thick, is 8.976 lbs., how much will 81 sq. in. of this thickness weigh ?
72 sq. in. (1/2 of 8.976 lbs.) = 4.488 lbs.
9 sq. in. (1/8 of 4.888 lbs.) = .561 lbs.
------------------------------------------
81 sq. in. = 5.049 lbs. "
My question:
Why was 1/2 and 1/8 used ?
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!
One square foot
= 1 foot by 1 foot
= 12 inches by 12 inches
= 12*12 = 144 square inches
The "breakdown method": (NOT a standard mathematical term -- but a valid method you are apparently learning....)
81 square inches = 72 square inches plus 9 square inches
72 square inches = 1/2 of 144 square inches, so 72 square inches weighs 1/2 as much as 144 square inches -- 1/2 of 8.976 pounds = 4.488 pounds
9 square inches = 1/8 of 72 square inches, so 9 square inches weighs 1/8 as much as 72 square inches -- 1/8 of 4.488 pounds = 0.561 pounds
Weight of 81 square inches of the material
= weight of 72 square inches plus weight of 9 square inches
= 4.488 + 0.561 pounds = 5.049 pounds
A summary without so many words to help see where the "1/2" and "1/8" came from:
81 = 72+9 = of 144 plus of 72
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