In part (a) of this question we are asked to calculate τmax. In order to do this we separate the cross section at the neutral axis and take the entire upper half (as shown in the cramster solution). When calculating τmax, the value for the thickness 't' is plugged in as '2x1/2'. I assume that this is because there are two sections each with a thickness of 1/2".
In part (b) the same value is plugged in for t when calculating the shear at point a. In this case i am wondering if one would be able to use the shear flow concept to solve this problem(knowing that the shear enters through the center at the top of the cross section and spreads away, going down each of the rectangular channels on either end, and then meeting again at the bottom rectangle at the center). We would use the entire upper rectangle, just as in the current solution, but only use (1/2") as t, and multiply the result by (1/2) since we only want the shear at point A. The result is the same numerically, but is this a proper approach?