The potato buyer first weighs the bell, and then puts these samples in water to weigh them, to tell the truth.

First of all, we must understand a common sense: the starch content of sweet potatoes is high and the purchase price is high. For potatoes of mass m:

Direct measurement

G=mg= density *V*g

In water, the measured apparent weight is the difference between gravity and buoyancy.

G'= G-F float =mg- density of water * g * v.

The difference between the two measurements is actually equal to buoyancy.

F float = density of water *g* volume of potato.

Because the density and g of water are fixed values.

If F floats small, potatoes will be small.

And because the mass is certain, the density is high.