Chapter 7 on the weighted average problem p 64 and p 67

[AnnaC666]

Hello,

I am currently revising Word Problems and the Chapter 7 on the weighted average problem.

I am quite confused between the difference in computation methodologies used for the weighting ratios.

On page 64 the ratios are computed by taking the distance between end points over the length whereas on the Kris P problem, the lenght aka 8 is not used at all.

Could you please kindly help me in understanding this point?

Thank you

Anna

[Sage Pearce-Higgins]

There's more than one way to solve these kinds of problems. The teeter-totter solution is usually easier than algebraic translation, but remember that these are methods to help you, not official solutions.

With the teeter-totter method, the distance of the strength of each ingredient from the mixture strength is the inverse of the strength of each ingredient in the mixture (in my classes, I explain it like a tug-of-war, each ingredient is trying to "pull" the mixture strength towards itself), which gives you the ratio directly. Take a look at PS 228 from OG 2017 and the Navigator explanation for this problem.

I don't understand your question about the Kris-P problem: I can see both solutions in my 6th Edition Word Problems Strategy Guide.