Question

The true density and bulk density of wheat grains are 1280 kg/m\(^3\) and 740 kg/m\(^3\), respectively. The porosity of the grains is ................ (rounded off to 2 decimal places).

Hint:

Porosity is the fraction of void space in a grain bulk and is always calculated using \(\varepsilon = (\rho_t - \rho_b)/\rho_t\).

Answer 1

Correct Answer: 0.4

Step 1: Formula for porosity.
\[ \varepsilon = \frac{\rho_t - \rho_b}{\rho_t} \] where \(\rho_t\) = true density, \(\rho_b\) = bulk density.

Step 2: Substitute values.
\[ \varepsilon = \frac{1280 - 740}{1280} = \frac{540}{1280} \] \[ \varepsilon = 0.421875 \]

Step 3: Round off.
\[ \varepsilon \approx 0.42 \; \text{or} \; 42.19% \] Final Answer: \[ \boxed{0.42 \; (42.19%)} \]