Sure. When the mash is done, pull the bag out and measure the wort. Then add enough water at 170F to make up 3.5 gallons and put the bag back in the pot. Stir it, pour the wort off, then add another 3.5 gallons and let it sit while you boil the first batch. You should get about 2/3rds of the total gravity in the first batch.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
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