Square based pyramid has a side length of $220$ (b) and a height of $105.$ Find the surface area.
I tried by "doing" Pythagorean theorem $110^2+105^2=s$
then i did the equation for surface area (total) $220^2+2\times s\times 220$ and the answer I got was ~$5$ m off the one in the textbook
How do I solve it?
Regardless of what numeric answer you get, your approach looks correct. The only typo I see is that you should be solving $110^2 + 105^2 = s^2$ to get the "height" $s$ of one of the triangular sides when you flatten it out. (You had $s$ instead of $s^2$ in your post). And then $4(220s/2)$ is indeed the total area of the 4 triangular sides.