Can I just switch the SIM card with the iphone?

I accidentally dropped my iphone 4 today at orientation, and it fell and the front screen and cracked. I spent all my money on what I need for school clothes, so I have to save up to replace it. Until then can I switch the SIM cards between my iphone 4 to my old iphone 3? Just to use until I get enough money to repair it. Thanks in advance

I'm only 15, so don't question about the money please.

No you can't do this directly because the sim card in the iphone 4 is a micro sim while the sim card in the iphone 3 is a mini sim (bigger than the micro sim) so you either buy a sim adapter which should look like: http://www.ebay.com/...1257682767
or make an adapter yourself here is how: http://www.ifixit.com/...ter/3183/1

Hope this helps
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