Explanation:

Let’s break it down:

- We have a uniform circular disc, diameter 9 cm, and a hole is cut at the centre. The question: what’s the diameter of the hole?

- Statement I says the weight drops by 30%. Statement II says thickness is 1 cm.

Now let’s look at what each statement does:

- Statement I:

- Knowing the weight drops by 30% tells you that 30% of the area (since uniform thickness) is removed.

- Since you know original diameter (and so area), you can set up the equation relating area removed to total area:

- p(r_outer)^2 - p(r_inner)^2 = area after the cut.

- You can solve for r_inner.

- You have everything you need here.

- Statement II:

- Thickness is 1 cm.

- But on its own, this doesn’t tell you how much of the disc is cut; you don’t get any information about the size of the hole, only the “height” of the disc.

- This by itself is not enough.

- Together:

- You don’t actually need both.

- Statement I alone does the trick.

So, you only need statement I. That’s option 1.

Your answer: option:1-1.

Short recap of options:

- Option 1: Can do it with one, not the other (this is the one!)

- Option 2: Either alone (not true)

- Option 3: Need both (not true)

- Option 4: Not possible even together (not true)