Question

what is the relative density of onion?

Answer 1

The relative density of onion is 0.91.

Answer 2

Relative Density of Onion =0.91

No unit

The values are approximate values as the size and mass of every piece if fruits and vegetables are different so their relative densities may also change.

Relative density is actually the density of the object ( fruits and vegetables in this case) with respect to the density of the water.
So you can see in the relative density the density of the substance is usually compared with the water density .And as we know that water density is 1g/cm3.
Hence just calculate the value of substance density by formula of m/v .

Also, mass can be calculated easily by weighing balance.