1. **Stating the problem:** Caitlin has 140 coins initially. She adds 15% more coins during the year. 2. **Formula used:** To find the number of new coins added, use the percentage increase formula: $$\text{New coins} = \text{Initial coins} \times \frac{\text{Percentage increase}}{100}$$ 3. **Calculate new coins:** $$\text{New coins} = 140 \times \frac{15}{100} = 140 \times 0.15 = 21$$ 4. **Calculate total coins at the end of the year:** $$\text{Total coins} = \text{Initial coins} + \text{New coins} = 140 + 21 = 161$$ 5. **Explanation:** Caitlin added 21 new coins, which is 15% of her original 140 coins. Adding these to the original amount gives a total of 161 coins at the end of the year.