# Circuit indicator problem

could anyone help me with this problem?

1. 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*

2. Homework Equations

V=IR

3. 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

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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?