Why does my new iPhone 4S lose battery so quickly?

Ok 2 days ago for my birthday I got an iPhone 4S from sams club under Verizon he batery drops rapidly and only last about 3 hours at the most till it dies the version I have 6.1.3 I hardly have any apps running I only have 3 at the most at one time why does my battery die so quickly and would changing settings help and if does tell me the effects please

Because all the task that you are running on the phone and apps

On your iPhone 4S, do you keep the apps on? If you do, all you need to do is double tap on the home button and then you will see all the apps you have used appear on the bottom part of your screen. Hold down on those apps until a minus sign show up on the top left of each app. Click on each app and each app and it will turn it off.