Mixtures and Alligation

intermediate26 min read

Weighted average and the alligation rule for mixing two ingredients of different price or strength, plus the repeated-replacement formula for a liquid drawn off and topped up with water.

What you will be able to do

Compute the price or strength of a mixture as a weighted average of its parts.
Use the alligation rule to find the ratio in which two ingredients are mixed.
Apply the repeated-replacement formula for a liquid removed and replaced with water.
Set up a dilution or concentration change by tracking the amount of the unchanged component.

What is inside this lesson

1What a mixture question asks
2Weighted average
3The alligation rule
4Repeated replacement
5Dilution and concentration by the unchanged part
6Worked example
7Common mistakes
8Quick revision
9Practice

The lesson itself is for members

Reading the 9 sections above, the worked examples and the practice set is free — the whole knowledge base is on the free plan, along with flashcards, private notes and Ask Onely.

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