yogurt ratios and percentages

an updated version

using fairly realistic data (in 2019 anyway)

a powerpoint is here

there are many other applications of Pearson's square technique (e.g. feed proportions) on the net
this is a weighted mean calculation
and it is reasonably straightforward to see how/why it works by working through a 'normal' calculation technique

I don't think students should learn it but it is used widely and it is of interest because (a) it's neat (b) it works and (c) it can be related to a 'normal' calculation