So the voltage across the series resistor will be \(4V\). In a series circuit, the current is the same at all points. So if the current in the LED is \(10 mA\), the current in resistor \(R\) is ...

When resistors are connected in series, the current through each resistor is the same. In other words, the current is the same at all points in a series circuit. When resistors are connected in ...