First find the total number of blueberries Mason has: 200 blueberries/carton * 3 cartons = 600 blueberries
Then divide the total number of blueberries by the number of blueberries per muffin: 600 blueberries / 10 blueberries/muffin = <<600/10=60>>60 muffins
Then add that number of muffins to the number of cinnamon muffins to find the total number of muffins: 60 muffins + 60 muffins = <<60+60=120>>120 muffins
Then divide the number of blueberry muffins by the total number of muffins and multiply by 100% to express the answer as a percentage: 60 muffins / 120 muffins * 100% = 50%
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