Horse A 48.5% place s.r
Horse B 42.5% place s.r
Horse C 37% place s.r
Horse D 33 % place s.r

If I were to take horses with those place strike rates in a box quinella, what would the expected strike rate of getting the quinella be?? assuming an average 10 horse race.

At a guess I would assume around 35 % but it may be lower than that.