If I put my Sim Card in another iPhone will?

My friend is offering me his new iPhone 5c for $70, if I buy it, can I take the SIM card out of my iPhone 4s and put it in the 5c to keep my number? I've already backed my phone up with icloud so I can restore the 5c and backup my contacts and apps. But the main question is: Will my iPhone 4 number stay on my 5c if I replace the sim card?

If its a gsm phone and your sim is gsm too then yes or if both are cdma then yes

First off lets strt with the SIM card dilemma.
There are three types of SIM cards. A SIM card, a micro SIM card, and a nano SIM card. That's from biggest to smallest. The 4s that you're currently using is a micro sim. The 5c that you're planning on using needs a nano sim. Therefore you can't just switch it that easily. What you want to do or need to do is go to your local mobile store (bell, Rogers, verizon, etc) tell them that you're switching to a 5c and that you now need a nano sim. They will go right ahead to transfer the same number on your MICRO to your new nano sim.
Btw this is if you're not on a contract, and you can switch from phone to phone or your contract is over
enjoy the new phone!

If you are handy go to youtube and type "cut micro sim to nano sim"