Thanks leo for your help...
1).If i split that string in to 2*5 led the current will drop to 500mA and voltage to 4.8 v for each led is it correct?
2).If yes what happens to led with that extra current (200mA) and voltage about 1.5 v??
3). if one of 2 fails suddenly the other ones could be damage by heavy amp and volt... is there any way for protection?