Two disc have their moments of inertia in the ratio 1:2 and their diameters are in ratio `2:1.` The ratio of their masses will be

Options

A. `1:4`
B. `1:8`
C. `3:4`
D. `5:4`

Explanation

To solve the problem, we need to find the ratio of the masses of two discs given the ratios of their moments of inertia and diameters.

### Step-by-Step Solution:

1. **Understanding the Given Ratios**:
- The moments of inertia of the two discs are in the ratio \( I_1 : I_2 = 1 : 2 \).
- The diameters of the two discs are in the ratio \( D_1 : D_2 = 2 : 1 \).

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