The correct answer is: "2/3" ; or write as: "2:3" .
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This is asumming that the mixture consists entirely of ryegrass and bluegrass and "nothing else".
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Explanation:
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If 40% of the mixture is ryegrass; and the rest of the mixture is bluegrass;
Then the entire mixture is 100% ;
and the bluegrass is: 100% − 40% = 60%.
There would be 40% ryegrass to 60% bluegrass:
40% / 60% = 4/6 = (4÷2) / (6÷2) = "2/3" ; or write as: "2:3" .
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