Table of Contents

• Prequiz
• 1: Three tricks division can do
• Section 1: Ratios and Fractions
• 2: Finding Ratios
• 3: More uses for Ratios
• Section 2: Proportions and Percents
• 4: Proportions and Percents: Parts of the Whole
• 5: Absolute amounts from percents
• 6: Parts and wholes
• Section 3: Percent Change
• 7: Measuring how things change
• 8: Percent Change is not a direct comparison
• 9: Units, units, units
• Section 4: Biology
• 10: What's in your milk?
• 11: An experiment

Parts and wholes

Earlier I said that proportions and percentages help you determine the relationship (or ratio) between the parts and the whole. I still stand by that statement, but...

It's important to carefully define what I mean by "part" and "whole"", and this can change depending on what question I'm interested in at the moment. Ah, what fickle creatures scientists are...

So, if I ask, what percentage of the carbs come from sugar, it helps to know that flour and sugar are the only sources of carbs in the cake, and therefore what I'm looking for is a relationship between sugar (the "part") and sugar+flour (the "whole").