South leads a spade to the 10; if it holds, he reenters his hand via another suit and leads another spade to the queen; if the 10 loses and he subsequently regains the lead in his hand, he likewise leads another spade to the queen. North-South will take three spade tricks if West has both the king and the jack (probability about 25% in the absence of any information), two if East and West have one each (50%), but only one if East has both (25%).
South leads a spade to the 10; if it holds, he reenters his hand via another suit and leads another spade to the queen; if the 10 loses and he subsequently regains the lead in his hand, he likewise leads another spade to the queen. North-South will take three spade tricks if West has both the king and the jack (probability about 25% in the absence of any information), two if East and West have one each (50%), but only one if East has both (25%).