If you make two holes in a can lid, the liquid pours faster (read details). Why?

Question

We had a can of milk cream. I made a small hole in lid and the milked poured slowly. My friend did something else: she made 2 diametrical opposite holes and then the milked poured fast.

Why does this happen?

Answer 1

Even if you're pouring a liquid from a single necked bottle, it will pour faster if you pour it in such a way that you allow at least a small channel of air to come into the bottle to displace the liquid.  The other answerers are correct in that when punching holes in a can, it works best to punch 2 holes as you have described.  What's more, while one of the holes can be made large for faster evacuation, the other can be a smal one since air isn't as viscous as the liquid.  

Answer 2

I agree that it's because the air enters the can, which allows the milk to come out faster.  The equalization of pressure allows for a faster liquid flow.

Answer 3

When you pour the liquid out, a vacuum forms inside the can.  The vacuum will try to pull the liquid or surrounding air back into the can, reducing the amount of liquid that is poured out.  Making a hole on the other side of the can allows air to flow into the can while the liquid still pours out.

Answer 4

Because when you only have one hole, while the liquid is pouring out there is also a lot of air rushing in to take up the space left behind by the liquid.

But when you have two holes, there is a lot of space for air to rush in one hole while all the liquid drains out of the other hole.