A recipe uses 2 1/4 cups of flour for 3 identical batches. The baker has 5 cups. After making 8 batches, how many more cups of flour are needed?
Student attempt
The student finds the total flour needed for 8 batches but submits that value as the final answer.
Likely misconception
The proportional reasoning is mostly intact. The miss is the final comparison: the baker already has 5 cups, so the question asks for the shortage.
Adaptive scaffold
Ask for two labels before calculation: total needed and already available. Then subtract only after the scaled total is known.
Next practice
Another ratio problem with an already-have amount, followed by one with irrelevant information to test transfer.