Bottle 1 contains a mixture of milk and water in 7 : 2 ratio and Bottle 2 contains a mixture of milk and water in 9 : 4 ratio. In what ratio of volumes should the liquids in Bottle 1 and Bottle 2 be combined to obtain a mixture of milk and water in 3 : 1 ratio?
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Use alligation method for mixture problems: $\frac{\text{Volume 1}}{\text{Volume 2}} = \frac{\text{Difference of higher and desired}}{\text{Difference of desired and lower}}$.