How do the animals deceive Mr. Whymper in Chapter Seven in Animal Farm?

By this time, the animals' lives are getting to be really
hard.  They don't have much to eat and they are having to work really hard.  But they do
not want the people around them to know this.  So they decide to fool the people by
fooling Whymper.  They are counting on Whymper to spread the word that the animals are
doing great.

So they do things like filling up the feed
bins with sand and then putting a bit of food on top to make it look like the bins are
completely full.  They have various animals talk about how the rations have been
increased at times and places where Whymper can hear.

That
way, they make him think the farm is doing fine.