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Standard practice

The factor is hidden in the target amount.

Equivalent ratios
cups of flourbatches
25
8?

Mei uses 2 cups of flour for every 5 batches at the cooking lab. The same relationship has to hold for a larger amount.

A ratio problem hides the factor inside a target amount. Dividing the target by the matching part of the base ratio reveals the factor. That factor, not the difference, scales the other part. Working backward uses the same relationship.

Problem 1 of 9. Activate, study a model, try guided items, work independently, apply, and reflect.

What is 2 × 4?

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