Moment of Inertia about y axis composite body

[engstrom2278]

Homework Statement

The moment of inertia (in4) about the y-axis is most nearly
(a) 39,500 (b) 37,600 (c) 38,700 (d) 36,400

Homework Equations

Iy(circle)= .25(pi)(r^4)
Iy(triangle)= (1/12)h(b^3)
parralel axis theorem= Iy=Iy'+A[d(x)]^2

The Attempt at a Solution

Iy(circle)= 39760
I don't know what to do with the subtraction of the triangles. Will they cancell each other out and the answer would be nearest (a)?

 

[tiny-tim]

welcome to pf!

hi engstrom2278! welcome to pf!

… I don't know what to do with the subtraction of the triangles. Will they cancell each other out and the answer would be nearest (a)?

are the triangles holes?

then treat them as having negative mass

(and no, they don't cancel each other, they combine)