Correct Answer - Option 3 : 66.67%

**Concept:**

**Dry Unit Weight(\(\gamma_d\)):**

It is a measure of the weight of solid particles per unit volume.

\(\gamma_d\) = W_{s }/ V

Where W_{s} = weight of solid particles, V = Volume of solid particles

Now the relationship between the specific gravity of solid particles, void ratio, and dry unit weight

\(\gamma_d = {G\gamma_w \over (1+e)}\)

where G = specific gravity of solid particles, e = void ratio

**Calculation:**

Given Data:

The mass of a chunk of moist soil = 20 kg

The dry density of soil(\(\gamma_d\)) = 1500 kg/m3

Specific gravity(G) = 2.50

The density of water(\(\gamma_w\)) = 1000 kg/m3

Using the relationship between the specific gravity of solid particles, void ratio, and dry unit weight

\(\gamma_d = {G\gamma_w \over (1+e)} \)

\(1500 = {2.50\times 1000 \over (1+e)} \)

\((1+e) = {2.50\times 1000 \over 1500} \)

e = 0.6667

**The void ratio is 66.67%**