Combine 1 1/4 c. sugar, salt and flour. Arrange half of the strawberries and rhubarb in pastry lined 9 inch pie pan. Sprinkle with half of the sugar mixture. Repeat with the remaining fruit and sugar mixture, dot with butter. Cover with other 1/2 of the pastry. Bake at 425 degrees for 40-50 minutes, or until rhubarb is tender and crust is browned.