Manuel needs 20 liters of the 8% and 5 liters of 20% mixtures to be mixed so as to get 30 liters of a mixture of water and 10% lemon juice.
Let x represent the amount of 8% lemon juice in liters and y represent the amount of 20% lemon juice in liters.
Since Manuel wants to produce a 30 liters mixture from 8% lemon juice and 20% lemon juice, hence:
x + y = 30 (1)
Also, Manuel wants 30 liters of a mixture of water and 10% lemon juice, hence:
8% of x + 20% of y = 10% of 30 liters
0.08x + 0.2y = 3 (2)
Solving equation 1 and 2 simultaneously; multiply equation 1 by 0.2 and subtract equation 2 from the result:
0.12x = 3
x = 25 liters
x + y = 30
25 + y = 30
y = 5 liters
Manuel needs 20 liters of the 8% and 5 liters of 20% mixture
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