Because 6 over 8 is between 7 over 8 and 5 over 8
let's recall that d = rt, distance = rate * time.
he went upstream to a distance "d", got tired and came back to his starting point, so he rowed back a distance "d" exactly.
we know the rates, we also know the trip took 2 hours, let's say on the way over he took "t" hours to get there, on the way back he lasted then "2 - t" hours.
![\stackrel{\textit{substituting on the 2nd equation}}{2t=8(2-t)\implies 2t=16-8t}\implies 10t=16\implies t=\cfrac{16}{10}\implies t=\cfrac{8}{5} \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{we know that}}{d=2t}\implies d=2\left( \cfrac{8}{5} \right)\implies \stackrel{\textit{3 miles and 1056 feet}}{d=\cfrac{16}{5}\implies d=3\frac{1}{5}}](https://tex.z-dn.net/?f=%5Cstackrel%7B%5Ctextit%7Bsubstituting%20on%20the%202nd%20equation%7D%7D%7B2t%3D8%282-t%29%5Cimplies%202t%3D16-8t%7D%5Cimplies%2010t%3D16%5Cimplies%20t%3D%5Ccfrac%7B16%7D%7B10%7D%5Cimplies%20t%3D%5Ccfrac%7B8%7D%7B5%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill%5C%5C%5C%5C%20%5Cstackrel%7B%5Ctextit%7Bwe%20know%20that%7D%7D%7Bd%3D2t%7D%5Cimplies%20d%3D2%5Cleft%28%20%5Ccfrac%7B8%7D%7B5%7D%20%5Cright%29%5Cimplies%20%5Cstackrel%7B%5Ctextit%7B3%20miles%20and%201056%20feet%7D%7D%7Bd%3D%5Ccfrac%7B16%7D%7B5%7D%5Cimplies%20d%3D3%5Cfrac%7B1%7D%7B5%7D%7D)
(2+sqrt2i)^-1 = 1 / (<span>2+sqrt2i)</span>
The density of the wooden block is 0.50625g/cm^3
<h3>Density of a wood</h3>
Density is defined as the ratio of the mass to volume of a substance. The formula for calculating the density of an object is expressed as:
Density = Mass/volume
Given the following parameters
Mass = 32.4grams
Volume = 4^3 = 64 cubic centimeters
Substitute
Density = 32.4/64
Density = 0.50625g/cm^3
Hence the density of the wooden block is 0.50625g/cm^3
Learn more on density here: brainly.com/question/6838128
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