An herbalist has 15 oz of herbs costing $4 per ounce. How many ounces of herbs costing $2 per ounce should be mixed with these 15 oz of herbs to produce a mixture costing $2.50 per ounce?

30 miles

step-by-step explanation:

we know that 60 seconds equals 1 minute and 60 minutes 1 hour

44 ft       60 sec     60 min     158400   ft

  *   *   =

1 sec       1 min       1 hour         hour

we know that there are 5280 ft per mile

158400   ft       1 mile         30 miles

  *   =

1   hour               5280 ft     1 hour

so in 1 hour   it can travel 30 miles