Mullah Nasruddin - Everyone knows how to investigate

Nasrudin gave his wife some meat to cook for guests. When the meal arrived, there was no meat. She had eaten it.
‘The cat ate it, all three pounds of it,’ she said.
Nasrudin put the cat on the scales. It weighed three pounds.
‘If this is the cat,’ said Nasrudin, ‘where is the meat? If, on the other hand, this is the meat – where is the cat?’