A man walks past a beggar every day and gives him $10 and that continues for a year. Then suddenly the daily donation changes to $7,50.
"Well," the beggar thinks, "it's still better than nothing."
A year passes in this way until the man's daily donation suddenly becomes $5.
"What's going on now?" the beggar asks his donor. "First you give me $10 every day, then $7,50 and now only $5. What's the problem?"
"Well," the man says, "last year my eldest son went to university. It's very expensive, so I had to cut costs. This year my eldest daughter also went to university, so I had to cut my expenses even further."
"And how many children do you have?" the beggar asks.
"Four," the man replies.
"Well," says the beggar, "I hope you don't plan to educate them all at my expense."