Rotational Motion Part 1

Let mass of the semi circular disc =M
Now assume a disc which is combination of two semi circular parts. Let I be the moment of inertia of the uniform semicircular disc. So 2I will be the moment of inertia of the full circular disc and 2M will be the mass.
‌⇒2I=‌

2Mr2

2

‌⇒I=‌

Mr2

2