Simple percentage ratio question using cacao percentages I have two dark chocolate bars, one has 55% cacao, the other 80%. I want to eat 20g of the 80%, then $x$ amount of the 55% bar that would have the same amount of cacao as the 20g of the 80% bar. I'm stumped. I'm guessing that the ratio between 55% and 80% has 80% as 1.4545... times more than 55%, so I'd simply multiply 20g times 1.4545..., or 29.1g of the 55% chocolate. Is this correct?

The simple way is to compute that you will eat $20 \cdot 0.8=16$g of cacao from the $80\%$ bar, so need to eat $\frac {16}{0.55}$g of the $55\%$ bar to get the same amount of cacao. That does give about $29.1$ grams of the $55\%$ bar.