question about blending batches and figuring out og


Is there a formula to figure out og based on blending known amounts and gravities of 2 worts?
I had a 3 1/4 gal batch of 1.038 and blended in 2 gals of 1.088. What would my blended og be?
The smaller gravity batch already had yeast pitched the day before, so I couldn't simply mix and measure. Thanks!
__________________
My wife is like a well crafted beer...bitter, yet sweet enough to balance perfectly!
