Figuring out how many revolutions a bicycle tire rotates for every pedal revolution.. I'm trying to figure out this problem on my assignment, goes as follows:

A bicycle works using two gears and a chain. Turning the pedals causes the front gear to rotate and the chain then causes the rear gear to rotate which cause the bike tire to turn. The bike has a front gear with radius of 4 inches and the rear gear has radius 2 inches. 

Determine the number of revolutions that the bicycle tire rotates when the pedals are rotated one revolution.

I truly have no clue.. Could someone help me out?

Any help or even clues are appreciated.

Thank you.
If you pedal one full circle, the chain moves by $2 \pi r$ ($r$ is pedal circle radius). The same length will go to the wheels (radius $R$): hence,
$$2\pi r = R \phi,\tag{1}$$
where $\phi$ is the angle (in radians) the cycle wheels rotate. From $(1)$, you get the angle the wheels rotate.
When front gear makes 1 rotation the rear gear will rotate 2 times of that. Ratio of the circumference(2×pi×R/ 2xpi×r) = 4÷2=2.
Rear gear attached  to back wheel so same rotation as rear gear