In one incident, a teen robbed an 18-year-old woman on an uptown No. 1 train Sunday afternoon.
Police say he was armed with a knife and demanded her Blackberry. The woman handed it over, and the suspect got off at the 231st Street station in Kingsbridge.
The second incident involved another teen and happened a few hours later at the same station.
The attacker tried to steal an iPhone, but the victim fought him off.
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