Answer: 300 ft
Step-by-step explanation:
This question is based on Indiana State Driving codes.
According to Indiana regulations, if you are going at a speed of 50 miles per hour or above, you should begin to indicate your desire to turn or change lanes at least 300 feet before you do.
This would give the person behind you ample time to react as they might be going at the same speed as you. The rules further state that the signal to use is that of the car but if it is damaged then hand signals would suffice.