A span is 8" or 0.67 foot. That is an informal measurement from the tip of the thumb to the tip of the pinkie on a average spread hand.
It is equal to to 72 because 2x6=12 and 3x2=6 and 12x6=72 or if you think this is to complicated, you can do 2x6=12, 12x3=36, and then 36x2, which then also gives you 72
Depends upon your personal "stride" ... the span of distance between each foot when walking normally.
That question cannot be answered without knowing the load on the beam.
6:1
Yes, a W-8X18 will carry the weight of a basement load wall 2X6 over a 200 feet span.
255
The factors that are involved are the span you are covering, the type of roof and the pitch of it. How you are bracing the rafters. Wider the span, wider the joist. 2x6 is usually enough for most house construction.
A span is usually a measurement of length, as in inches or feet, not of time. However, some fantasy novels etc uses span for time; A span is an eleven day week.
189....
A span is 8" or 0.67 foot. That is an informal measurement from the tip of the thumb to the tip of the pinkie on a average spread hand.
3
12
A nominal 2x6 baord is actually 5.5" wide. 5.5"/12"=0.45833ft => 0.45833ft x 300ft = 137.5 sq-ft
Usually there are 10 in a bundle.
250 Feet
You must also take in consideration the width of the building. For instance a 12'x16' building you would use 2x6 rafters and a 2x8 beam with collar ties every 4'.