Front
Ring
Front
Teeth
Rear
Cog
Ratio
S2225 
S2223 
S2221 
S2219 
M32251.28
S22171.29
M32231.39
S22151.47
M32211.52
S22141.57
M32191.68
S22131.69
L44251.76
S22121.83
M32171.88
L44231.91
L44212.09
M32152.13
M32142.28
L44192.31
M32132.46
L44172.59
M32122.67
L44152.93
L4414 
L4413 
L4412 
  Michele's road bike has a triple chain ring in front with 44, 32, and 22 teeth. This is a mountain bike crank that darn near works perfectly with her Shimano 105 front deraileur. This table demonstrates the combinations, in order, producing actual ascending gear ratios. Just for fun, and because she asked. This is to show that to truly find the perfect cruising gear at a particular speed, you need to considert chaning not only the rear cog, but also the front chain ring in order to hone in on that perfect gear.

Suffice to say that:

if you are in the granny gear in front,
  the middle in back,
    and you anticipate going faster:

    it is time to switch to the middle ring in front
    and go back to low gears (big cogs) in back.

conversely:

if you are in the middle ring in front,
  the lowest/easiest gears in back (big cogs),
    and you anticipate going slower:

    it is time to switch to the granny gear in front
    and go up to some higher gears (middle cogs) in back.