
William W. answered 02/23/20
Math and science made easy - learn from a retired engineer
Let's first convert the diameter into cm and the mass into grams. There are 2.54 cm per inch and there 0.00220462 lb in 1 gram so:
Mass (m) equals density (ρ) times volume (V) or:
m = ρV
Volume (V) of a cylinder (wire is the shape of a very long skinny cylinder) is pi times radius (r) squared time the height or, in this case, length (L) so:
V = πr2L
And radius is diameter (d) divided by 2 or
r = d/2
So V = π(d/2)2L and plugging this into the mass equation:
m = ρπ(d/2)2L
Solving that equation for L we get:
L = m/(ρπ(d/2)2) = 725.7486551/(8.92π(0.1290828/2)2) = 6217.198745 cm
Since there is 1 meter in 100 cm we divide the answer by 100 to get meters.And since there are 3 significant figures in the givens, we also round to 3 sig figs giving us 62.2 meters