To maintain the freshness and beauty of your arrangement of 10 pink tulips and 10 white tulips in a glass vase, follow these flower care tips:

1. **Trimming**: Upon receiving the arrangement, trim the stems of the tulips at an angle with sharp scissors. This helps them absorb water more efficiently.

2. **Water**: Fill the glass vase with clean, room temperature water. Ensure that the water covers at least 2-3 inches of the stems.

3. **Remove Leaves**: Remove any leaves from the lower part of the stems that will be submerged in water. This prevents bacterial growth and keeps the water clean.

4. **Placement**: Display the arrangement in a cool area away from direct sunlight, heat sources, and drafts. 

5. **Water Change**: Change the water every 2-3 days to keep it fresh and clear. Before changing the water, recut the stems at an angle to maintain their ability to absorb water.

6. **Flower Food**: Add flower food to the water to nourish the tulips and prolong their freshness. Follow the instructions on the flower food packet for the correct dosage.

7. **Pruning**: Remove any wilted or spent blooms from the arrangement to maintain its appearance and encourage new growth.

8. **Cleaning**: Regularly clean the glass vase to remove any dirt or bacteria buildup, which can affect the longevity of the flowers.

By following these care tips, you can ensure that your arrangement of pink and white tulips remains vibrant and beautiful for as long as possible, allowing you to enjoy its elegance and charm.