A room heater is rated 400 W, 220 V. If the supply voltage drops to...

The resistance of the room heater is given by $R = \dfrac{V^2}{P}$

Substituting the rated values, $R = \dfrac{220^2}{400} = \dfrac{48400}{400} = 121 \Omega$

When the supply voltage drops to $V' = 200$ V, the power consumed is $P' = \dfrac{V'^2}{R}$

$P' = \dfrac{200^2}{121} = \dfrac{40000}{121} \approx 330.57$ W

Therefore, the power consumed is approximately $331$ W.

Answer: $331$ W