How old is a 20inch rainbow trout?

The age of a 20-inch rainbow trout can vary significantly based on environmental factors, growth rates, and habitat conditions. Generally, in favorable conditions, a rainbow trout may grow about 1 inch per year, suggesting that a 20-inch trout could be around 5 to 7 years old. However, in optimal environments, some may grow larger and faster, potentially making a 20-inch trout older than 7 years. Ultimately, age estimates can differ widely depending on local conditions and food availability.