Thread: Please can someone check my mechanics work?

The questions are on this link, there are 3 of different types and I have written the answers alongside them - or at least, what I think the answers are. Sorry I cannot provide working because this was an exam that I did today so I obviously had to hand all of my working in to be examined

Regardless, I hope you can help me and will be very thankful if you can.

Is there nobody who is able to check this? Shall I post my working as to how I got those answers so you can check them?

I have a suggestion or two: break this post up into smaller chunks. No thread should really be concerned with more than two problems, preferably one.

Okay then how about question 9:

I made a table of values:

Rectangle: [Area: 80] [Distance from AD: 4] [Distance from AB: 5]
Triangle: [Area: 9] [Distance from AD: 3] [Distance from AB: 3]
Lamina: [Area: 71] [Distance from AD: X bar] [Distance from AB: Y bar]

Then take moments: 71Xbar = 80x4 - 9x3 = 347, Xbar = 4.13 (2dp)
and for the other, 71Ybar = 80x5 - 9x3 = 373, Ybar = 5.25 (2dp)

I think I just realised that my answwers were wrong! I think I added when I should have subtracted. The angle therefore is wrong. Do you agree with this working?