Question

What is the number of grains of rice in the 40 mL sample? Show all of your work using dimensional analysis.

Answer 1

The number of grains of rice in the 40 mL sample : 880 grains

Further explanation

Given

from recorded data:

mass of 20 grains rice = 0.4 g

mass beaker = 29.5 g

mass beaker+rice=47.1 g

mass only rice = 17.5 g

Required

the number of grains of rice

Solution

Maybe if we use a digital scale with high resolution accuracy we can get the mass of 1 grain of rice

But we still use existing data

To determine the mass of rice in the beaker, we just need to find the difference between the mass of the beaker + rice - beaker, or we can set the scale to zero before we add rice to the beaker.

If we look at this difference, the mass of the rice in the beaker should be :

47.1-29.5 = 17.6 g

Since the data shows that 20 grains of rice mass 0.4 g, so 17.6 g of rice contains:

$\tt 17.6~g\times \dfrac{20~grains}{0.4~g}=880~grains$