A 25 watt ,220 V and a 100 watt ,220V bulbs are joined in series and connected to the mains. Which bulb will glow brighter

Resistance of 25 watt bulb
${\mathrm{R}}_1=\frac{{\mathrm{V}}^2}{\mathrm{P}}=\frac{(220{)}^2}{25}=1936\mathrm{\Omega }$
Resistance of 100 watt bulb
${\mathrm{R}}_2=\frac{{\mathrm{V}}^2}{\mathrm{P}}=\frac{(220{)}^2}{100}=484\mathrm{\Omega }$
Brightness of bulb is directly proportional to $i^{2}R.$Since same current is flowing through the bulbs , 

25 watt bulb will glow brighter.