To determine how much baking soda Lisa should add to 9 lbs. of flour, we can set up a proportion based on the amount of baking soda used for 6 lbs. of flour.
The ratio of baking soda to flour can be calculated as follows:
- For 6 lbs. of flour, Lisa uses 2 tsp of baking soda.
- Therefore, the amount of baking soda per pound of flour is \( \frac{2 \text{ tsp}}{6 \text{ lbs}} \).
Now we can find out how much baking soda is needed for 9 lbs. of flour:
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Calculate the amount of baking soda per pound: \[ \frac{2 \text{ tsp}}{6 \text{ lbs}} = \frac{1 \text{ tsp}}{3 \text{ lbs}} \]
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Now multiply by 9 lbs to find the amount for 9 lbs: \[ 9 \text{ lbs} \times \frac{1 \text{ tsp}}{3 \text{ lbs}} = 3 \text{ tsp} \]
Thus, Lisa should add 3 tsp of baking soda to 9 lbs. of flour.