1. **State the problem:** Kelsey knitted a scarf with green and blue stripes. The ratio of green to blue stripes is 4 to 5. We know she knitted 48 rows of green stripes and want to find how many rows of blue stripes she knitted. 2. **Write the ratio:** The ratio of green to blue rows is given as $4:5$. 3. **Set up a proportion:** Let $x$ be the number of blue rows. Then, $$\frac{4}{5} = \frac{48}{x}$$ 4. **Solve for $x$:** Cross multiply: $$4 \times x = 5 \times 48$$ $$4x = 240$$ 5. **Divide both sides by 4:** $$\cancel{4}x = \frac{240}{\cancel{4}}$$ $$x = 60$$ 6. **Answer:** Kelsey knitted **60 rows** of blue stripes. This means for every 4 green rows, there are 5 blue rows, and since there are 48 green rows, the blue rows are proportionally 60.