Venu and his father were discussing how their ages compare over time. Venu's father said, "I am 48 years old now, and you are 21 years old". Venu became curious and started thinking about how their age ratio changes at different times - in the past and future.
Based on the situation, answer the following questions:
1. What is the ratio of present age of Venu's father to Venu's present age?
2. What was their age ratio 9 years ago?
3. What will be the ratio of their ages after 9 years?
4. What was the ratio of their ages when the father was 30 years old?