David drove 70 miles in the first 1 ¾ hours of his trip. how much longer should it take him to drive an additional 120 miles if he drives at the same average speed?

Let us first calculate the average speed of David,

Av speed = Distance traveled/ Time taken

We have, distance = 70 miles

Time = hours = 1.75 hours

Av speed =

= 40 miles/hour

Another 120 miles will be traveled in time, t = 120/40 = 3 hours

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.