Butterfly Five Ways

Run five quick reps. Compare: 3/7 vs 5/12. Cross products: 3 × 12 = 36, 7 × 5 = 35, so 3/7 wins. Add: 1/6 + 3/8. Cross to 1 × 8 + 6 × 3 = 26 on top, 6 × 8 = 48 on bottom: 26/48 = 13/24.

Subtract: 5/9 − 1/6. Cross: 30 − 9 = 21 on top, 54 on bottom: 21/54 = 7/18. Convert units: if 3 cups = 48 tablespoons, how many in 2 cups? Set 3/48 = 2/x, so x = 96 ÷ 3 = 32. Scale a recipe: 2/3 cup sugar for 4 people. For 6, set 2/3 ÷ 4 = x ÷ 6, so x = 6 × 1/6 = 6/6 = 1 cup.

Five reps and the butterfly becomes your default move.