Three resistors with electrical resistances R1 = 10 Ohm, R2 = 20 Ohm and R3 = 5 Ohm are connected

Three resistors with electrical resistances R1 = 10 Ohm, R2 = 20 Ohm and R3 = 5 Ohm are connected in series in the electrical circuit. The voltage across R1 is 6 V. Determine the voltage across R3 and the total voltage across the three resistors.

Given: R1 = 10 ohms, R2 = 20 ohms and R3 = 5 ohms U1 = 6 V
Find: U3-? Uob-?
Rob = R1 + R2 + R3 = 10Ω + 20Ω + 5Ω = 35Ω
I1 = U1 / R1 = 6V / 20Ω = 0.3A
I1 = I2 = I3 = Iob
U3 = I3 * R3 = 0.3A * 5Ω = 1.5V
Uob = Rob * Iob = 35Ω * 0.3A = 10.5V
Answer: 1.5V, 10.5V