Riya is preparing lemonade for a school event. She notices that for 5 people, she needs 4 lemons. She wants to serve lemonade for more guests in the same proportion.
Answer the following questions:
1. For 15 people, how many lemons will Riya need?
2. For 25 people, how many lemons will Riya need?
3. If Riya has 20 lemons, how many people can she serve?
4. If Riya uses 40 lemons, how many people can get lemonade?