Power dissipated across any resistance is given by
[tex]P = i^2 R[/tex]
now it is given that when one resistance of value 3 ohm connected the power dissipated is 4 Watt
now another identical resistance of same value is connected then the current will reduce to half of its initial value.
now power across any one resistance is given by
[tex]P = (\frac{i}{2})^2 R[/tex]
So now we will have
[tex]P = \frac{i^2}{4}*R[/tex]
So now the power will become 1/4 times of initial power
So now the power will be
[tex]P = 1 Watt[/tex]