When two resistors of $R \ \Omega$ value are connected in parallel,what is the equivalent resistance?

Three electric bulbs of $200\,W, 200\,W$ and $400\,W$ are shown in the figure. The resultant power of the combination is ................ $W$.

Forty electric bulbs are connected in series across a $220\, V$ supply. After one bulb is fused,the remaining $39$ are connected again in series across the same supply. The illumination will be

$A$ ring is made of a wire having a resistance $R_0 = 12 \,\Omega$. Find the points $A$ and $B$,as shown in the figure,at which a current-carrying conductor should be connected so that the resistance $R$ of the sub-circuit between these points is equal to $\frac{8}{3} \,\Omega$.

$A$ heater coil connected to a supply of $220 \ V$ is dissipating some power $P_1$. The coil is cut into half and the two halves are connected in parallel. The heater now dissipates a power $P_2$. The ratio of power $P_1 : P_2$ is

Three resistors of equal value $R$ are arranged in the different combinations shown below. Arrange them in increasing order of power dissipation.