Solutions to The Lateral thinking Test

The son put his hand into the moneybag and drew out a pebble. Without looking at it, he fumbled and let it fall onto the pebble-strewn path where it immediately became lost among all the other pebbles.

'Oh, how clumsy of me,' he said. 'But never mind, if you look into the bag for the one that is left, you will be able to tell which pebble I picked.'

Since the remaining pebble is black, it must be assumed that he had picked the white one. And since the moneylender dared not admit her Dishonesty, the son changed what seemed an impossible situation into An extremely advantageous one.

Here is an alternate answer, sent in by one of our visitors:

The son could pick a pebble out of the bag and conceal it in his hand and pour the remaining black pebble out onto the ground for everyone to see.  The old lady could choose to “save face” by saying it was obvious then that the one the son was holding was white.