To reduce the original current by half is only possible by doubling the total resistance of the circuit.
Setting the restance of each resistor to 1 unit, the total resistance is at the beginning equal to 1.5 units. This is due to the fact that the total resistance of 2 parallel resistors of equal size Rp is half of the single resistance Rp.
To reach 3 units as total resistance for the complete circuit, R2 and R3 have to be increased by a factor of 4. This will add 2 units to R1, resulting in a total resistance of 3 units for the complete circuit.

back