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Ok I am completely stuck on this question, i have some idea on how to do it and know it is to do with moments but i can't figure out where to take the moments.

Calculate the value of Y-Bar for the I-section shown below, where Y-Bar is the vertical height of the centroid of the section above its base.

Y-Bar x Area of shape = XA * AA + XB * AB + XC * AC

Y-Bar x Area of shape = XA * AA + XB * AB + XC * AC

so

Y-Bar x 12,000 = XA * 3600 + XB * 3600 + XC * 4800

Y-Bar = (XA * 3600 + XB * 3600 + XC * 4800) / 12,000

I have gone through my notes and several textbooks but i can't work out where to take the moments to get the XA, XB and XC values. Its probably obvious but if someone can give me a nudge in the right direction it would be appreciated.

## Homework Statement

Calculate the value of Y-Bar for the I-section shown below, where Y-Bar is the vertical height of the centroid of the section above its base.

## Homework Equations

Y-Bar x Area of shape = XA * AA + XB * AB + XC * AC

## The Attempt at a Solution

Y-Bar x Area of shape = XA * AA + XB * AB + XC * AC

so

Y-Bar x 12,000 = XA * 3600 + XB * 3600 + XC * 4800

Y-Bar = (XA * 3600 + XB * 3600 + XC * 4800) / 12,000

I have gone through my notes and several textbooks but i can't work out where to take the moments to get the XA, XB and XC values. Its probably obvious but if someone can give me a nudge in the right direction it would be appreciated.