Once the Wangarans got to the site they looked at the items and left gold. The amount of gold depending on how much they felt the items were worth.
They beat a drum to let the traders know their offer was proposed.
The Wangarans went back home giving the traders time to view the offer.
The traders traveled back to the river bank to see if the amount of gold left was acceptable
If the traders agreed with the wangarans on the amount of gold left they would take it and the trade would end. If the traders did not agree they wouldn't take the gold and would wait for the Wangarans to leave more. This went on until they agreed on an amount.
Advantages of silent trade were that it allowed people who spoke different languages to conduct trade. It also allowed the Wangarans to guard the secret of where the gold mines were. This kept the value of gold high.