First figure out how many times 15 can go into 90. 90/15=6 So you now know that it takes him 6 times the amount of time. So you would multiply 4 and 6 4*6=24 It will take the bird 24 hours to travel 90 miles. Hope this helps.
240 minutes would be 4 hours. 15 miles times 6 is 90 miles. so you take 240 and times it by 6. which equals, 1440. so it would take 1440 minutes to fly 90 miles. hope this helps!