How do you escape % when formatting a string?

[Terry Reedy]

"erikcw" <erikwickstrom at gmail.com> wrote in message 
news:1175543459.131630.96650 at y80g2000hsf.googlegroups.com...
| Hi,
|
| I'm trying to format a string like so:
|
| string = "You have a 75% chance of success with %s, don't use %s" %(a,
| b)
|
| This gives me:
| TypeError: not enough arguments for format string
|
| I've tried 75\%, but that doesn't seem to help.  What am I missing?

The reference manual?