How Do You Calculate Current in a Half-Full Gasoline Gauge?

[potato987]

could anyone help me with this problem?

Homework Statement

An automobile gasoline gauge is shown schematically in Figure 27-61. The indicator (on the dashboard) has a resistance of 10 . The tank unit is a float connected to a variable resistor whose resistance varies linearly with the volume of gasoline. The resistance is 200 when the tank is empty and 30 when the tank is full.


*Find the current when the tank is half-full*

Homework Equations

V=IR

The Attempt at a Solution

the current when the tank is empty is 12=I*200. so i multiplied that by two to get the answer but it was incorrect. i also tried to plug 15 into the equation since it's half of thirty but that too was wrong

 

[mikelepore]

First let's make a little chart to describe the variable resistor:

200 ohms ... tank empty
? ohms ... tank half-full
30 ohms ... tank full

What number should I replace those question marks with?