You're dealt a pair of 9s. The dealer shows a 3. Split or play it as one hand? Basic strategy answers:
Against a dealer 3 (37% bust chance), splitting 9s turns one mediocre total into two playable hands while the dealer is vulnerable. With double-after-split allowed, you also keep the option to press each new hand — that's where the split profit comes from.
Note the famous 9-9 exception: against a 7 you stand, because your 18 beats the dealer's likely 17. Against 8 or 9 you split again. It's the trickiest row of the whole chart.