Ruth's two cousins ate a total of 2 x 1 = <<2*1=2>>2 sandwiches.
So there were 3 + 2 = <<3+2=5>>5 sandwiches left before her two cousins arrived.
Before her first cousin arrived, there were 5 + 2 = <<5+2=7>>7 sandwiches.
Ruth and her brother had 1 + 2 = <<1+2=3>>3 sandwiches altogether.
Therefore, Ruth prepared 7 + 3 = <<7+3=10>>10 sandwiches."
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