1. The problem statement, all variables and given/known data Just studying statics in my first year of university and i do not understand the centroid topic at all. The question goes like this, given a equation y=x^2 , and the x-axis is 0 - 4 , with the lower portion of the graph is highlighted. It is given by diagram but sorry I don't have scanner so can't provide the diagram, but i think the info i gave is enough to illustrate that simple graph. The question ask to find the centroid of it. 2. Relevant equations The equations i know that i have to use is X-dash and y-dash formula. x-dash formula is (let assume | is integration) "|xdA within 0-4 divided by |dA, (A=|ydx)" and "|ydA within 0-16 divided by |dA, (A=|xdy)". 3. The attempt at a solution I go through all the equations and I found X-dash is 3 which I think is correct, but my y-dash is 9.6, which is doubled of the answer provided to me, 4.8... I don't understand what's wrong with my calculation ? p/s : I asked my lecturer and he said the |ydA shud be |(y/2)dA , but why ? Please do help me because my exam is coming and I still dun understand this small parts of statics. Thanks for any help.