A tap can fill an empty tank in 48 minutes where as another tap can empty the full tank in 2 hrs. If both the tap are opened at 11 : 40 am, when will the empty tank be filled

LCM of $(48,120)$ is 240 UNITS

$\begin{array}{l}48\to \text{\hspace{0.17em}240/48→5→FILLS \hspace{0.17em}}+5 UNITS/MINUTE\\ 120\to 240/120\to 2\to EMPTY -2 UNITS/MINUTE\\ \text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}WHEN BOTH OPENED TOGETHER IT FILLS +5-2=+3 UNITS/MINTE}\\ TO COMPLETE 240 UNITS ,IT TAKES 240/3=80 MINUTES\end{array}$

$IT FILLS AT 11:40+80\min =1pm$