Amy needs 5.0 V for some integrated circuit experiments. She uses a 7.5 V battery and two resistors to make a voltage divider. One resistor is 310 . She decides to make the other resistor smaller. What value should it have?

Answer 1

She wants 2/3 the voltage across one resistor (the larger), and 1/3 across the smaller.

So, the smaller must be 1/2 the larger, since V=IR and the same current flows through both resistors.