The relationship between Thrust, Fuel flow, Airspeed, RPM, Altitude, ambient pressure

[manucordier]

Hi,

Does anyone have a clear explanation to understand the logic behind the answers to the 3 following questions (JAA ATPL exam, FlyAround):

Question 1 :

At constant thrust and constant altitude the fuel flow of a jet engine:

Answer: increases slightly with increasing airspeed.

Question 2 :

At a constant Mach number the thrust and the fuel flow of a jet engine:

Answer: decreases in proportion to the ambient pressure at constant Temperature.

Question 3 :

The thrust of a jet engine at constant RPM :

Answer: increases in proportion to airspeed

Thank you for your help,
Emmanuel Cordier.