Ok, so here's what we have got.

✨ For the pipe

r₁=d₁/2=2/2=1 m

r₂=d₂/2=1.5/2=0.75 m

✨For the cuboid [tank]

l=150m

b=100m

h=3m [because we only need the volume till the height of 3 meters]

Now, the volume of the cuboid [tank] is lbh= 150*100*3 meters

=45000 m³

then now we know that speed=distance/time, where we have been given the speed. [please don't notice my grammar mistakes]

here, speed of water is 15 km/h and we are given the integers in meter, so we are going to convert the speed into the meter/second first.

and the speed is......

=15*1000/3600

=4.167 meters per second.

Now, the water flows on 4.167 meters per second. and the volume of the tank is 45000 m³. Now, we have got the speed and the volume. It was all okay till here. But from here, it the question made me think.

[I'm not sure if I'm right or wrong from ahead though I'll try]

so, to find the time, we might divide the area by the speed. [speed=distance/time, but here what we have got is the area, that's why I'm confused]

so, using the area in spite of the distance, here's what we have got...

time=area/speed

=45000/4.167

=10799.13

=10800 seconds

=**3 hours**

[I'm going to ask this question to my maths teacher today evening to make sure if I'm right or now, till that time, this was my try.]

hope it helped.

Y'know it was an **INSANE! **question for me. Really, you've got a nice question. ^_^