David Chose Five Stones

"Is that why David took five stones from the brook? One was enough for Goliath."

-David C. Brown (Commenting to Goliath had a Brother?)

This is one things that the bible doesn't give any answer to, but by looking at a few verses, I can make a few guesses as to why he might have chosen to collect five stones instead of one using the info that I have been given.

Then he took his staff in his hand, chose five smooth stones from the stream, put them in the pouch of his shepherd's bag and, with his sling in his hand, approached the Philistine.
1 Samuel 17:40

While it is a popular belief that the remaining four stones were used for Goliath's brothers, there are a few problems with this idea.

1. Goliaths brother were killed  later on in David's lifetime, and it makes no since to keep those stones, waiting for killing the older brothers.
2. There are a total of 6 brothers mentioned in the two passages. (Ishbibenob, Sippai, Lahmi, Saph, the 12 fingered man, and Goliath) That would be a total of 6 stones if they were to represent Goliaths brothers.
3. David didn't kill ANY of Goliath's brothers. (David was only battle  were Ishbibenob died (2 Samuel 21:15-17). That means he didn't even see four of the giants die.)

Here are a few reasons that are more likely.

• Just in case...

I am sure David was scared before be killed Goliath. Yes, he was full of faith, but he could have a few extra rocks with him in case he missed. Even if he didn't have any doubt, he would still know that sometimes you have to hard fight to win. David might have been anticipating a miss or two. Or he might have several in case the first rock hit Goliath, but didn't take him down.

• Afterwards
  

Even if David knew he would kill Goliath on the first strike, there's still what happens after. He didn't know how the Philistines would respond to the death of their hero, and he might have had a few rocks on him just in case they tried to attack him.

• Five different stones types

Another thing I've heard before is that David selected five different types of rocks (Hard ones, softer ones, shinier ones, ones made of different substances etc.) and then trusted God to have him grab the type of rock God wanted into his sling.

I can't answer your question with a simple yes or no because the scripture doesn't say. As long as you idea is within what the bible tells us, anything goes for this particular instance. 

Photo Credit:
http://baptistsermon.wordpress.com/2011/07/19/11/