Problem
Wyatt uses 3.15 cups of flour in a recipe that makes 9 shortcakes. Cora uses 2.4 cups of flour in a recipe that makes 8 shortcakes. How much more flower per shortcake is needed for Cora's recipe? (A) 0.05 cup (C) 0.25 cup (B) 0.20 cup (D) \( 0.50 \mathrm{cup} \)
Solution
Step 1 ：\( \frac{3.15\,\mathrm{cups}}{9\,\mathrm{shortcakes}} = f_W \)
Step 2 ：\( \frac{2.4\,\mathrm{cups}}{8\,\mathrm{shortcakes}} = f_C \)
Step 3 ：\( f_W - f_C = \Delta f \)
