A certain string has a mass of 120 g and a length of 40 cm. Consider the quantity 3 = 120/40.

1. Give the name of the quantity if there is one.

2. What is the interpretation of the quantity in this context?

3. Use the interpretation to find the mass of 7 cm of the same kind of string.

3 = 120/40 = >

1. Name of the quantity: constant of proportionality

2. Interpretation in the context: It is the the ratio of mass to length of the string. You can call it the linear density of the string, because it is mass / length, whose units are g / cm. It means that every cm of string has a mass of 3 grams.

3. Mass of 7 cm

7 cm * 3 g/cm = 21 g.