Resistors usually come in standard values, and I for one don't have all of those.

But they can be put together in serial and/or parallel to make almost any value.

Here is a link showing voltage divider and formula. That's a really good site, you might bookmark it.

http://electronicsclub.info/vdivider.htmIf R1 is 2000 ohms (2 1K's in series for me) and R2 is 4700 ohms the Vo would be 3.5V.

Notice that Voutput = Vsource x ( R2 / ( R1 + R2 ))

( R2 / ( R1 + R2 )) gives the fraction of source voltage that output voltage will be independent of source.

I used 3 x 4.7K resistors to make a 1/3 drop by putting 2 in series to make R2 and the other to be R1.

My output voltage is 2/3 which for 5V is 3.3V. To get 3.5 I varied the ratio so that less goes straight to ground.

My output current runs through the 4.7K resistor so it will be less than if no divider is present but I don't need much current, it is for voltage-leveling a serial pin on a 3.3V chip to a 5V Arduino. I used 4.7K's so that less current would flow to ground than with lesser ohms.

That may be more resistance than you want, the 2K-4.7K example above is half as much. Still, you may need to play around to get just what you want/need.