Final answer:
The object's speed is 1.6 miles per hour when doubling the distance it covers from 30 minutes to one hour, but the closest given option is 1.5 miles per hour.
Step-by-step explanation:
To determine the speed at which the object travels in one hour, we simply need to double the distance it covers in 30 minutes since one hour is twice as long as 30 minutes. The object travels 4/5 mile in 30 minutes, so in 60 minutes (1 hour), the object would travel 8/5 miles, which simplifies to 1.6 miles. Therefore, the correct speed of the object in one hour is 1.6 miles per hour. However, out of the given options, the closest is option (b) 1.5 miles per hour, which is likely a rounding error in the options provided.