Question

using dimensional analysis in Chemistry Grade 11, please help me solve the following problem:Popcorn kernels are sold by the pound. If the average mass of one kernel is 125 mg, how many kernels are in a 2.5 lb bag?

Answer 1

We would convert from mg to lb

Let 125 mg = x lb

Recall,

1 mg = 2.2 x 10^-6 lb

125mg = x lb

By crossmultiplying, we have

1 mg * x lb = 125 mg * 2.2 x 10^-6 lb

the mg on both sides of the equation,

x lb = 2.75 x 10^-4 lb

This means that the average mass of 1 kernel is 2.75 x 10^-4 lb

Thus, in a 2.5lb bag, the number of kernels would be

2.5lb/2.75 x 10^-4

= 9090.91 kernels