### Comment:
Use delta of the 2515 put. 
  
 Probability of expiring OTM is roughly equal to delta. 
  
 Probability of touch is roughly twice delta. 
  
 So if delta for the 2515 put is around .02 to .03 then there’s a 97-98% chance that put expires worthless. But there’s a 4-6% chance of SPX touches 2515 before close on 1/18. 
  
 Check whatever delta is for SPX though. I’m looking at 251.5 SPY which isn’t exactly equal to SPX.

### REPLY:
Dang I love these short hand methods for estimates do you know a good resource for finding a collection of short hand methods for calculating things like this or gamma/theta scalps etc.

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