What is the change in indicated altitude when setting the altimeter from 29.15 to 29.85?

When an altimeter is set to a lower pressure setting, such as from 29.15 inches of mercury (inHg) to 29.85 inHg, the indicated altitude will increase. This occurs because the altimeter measures the atmospheric pressure and translates it into an altitude based on the standard atmosphere model.

The difference in pressure between the two altimeter settings can be calculated by finding the difference in inches of mercury: 29.85 - 29.15 = 0.70 inHg. Since each inch of mercury corresponds to approximately 1,000 feet of altitude change, this increase in settings indicates that the indicator will reflect a higher altitude. Specifically, for every 1 inHg change, the altitude changes by about 1,000 feet, making a 0.70 inHg increase in the altimeter setting approximately a 700-foot increase in indicated altitude.

Therefore, adjusting the altimeter in this manner results in an increase of 700 feet in indicated altitude, making this the correct answer.