First, let's figure out how many miles the plane can fly in 1/4 hour. Since this is half of 1/2 hour, it can fly half of 105 miles, which is 52.5 miles. Next, we need to know how many miles it can fly in one hour. Since it flies 105 miles in 1/2 hour, it flies twice that (210) miles in one hour. So then in 1 and 1/4 hours, it flies 210+52.5 miles.