posted by charlie .
In a 9V circuit, all the resistors are 20 or 40 kilo Ohms.
Convention says that calcs should therefore be quoted to 1 sig fig, since the volts are the least accuracy.
2 seems better though. Any ideas?
Carrying an extra sig. fig. is always a good idea, since the first significant digit of whatever you are computing (such as current in this case) may be a low one like 1 or 2.
1 +/- 0.5 is precision, but 9 +/- 0.5 is 0.55% precision.