Answered

a mixture of 3% disinfectant solution is to be made from 5% and 2% disinfectant solutions. how much of each solution should be used if 21 gallons of 3% solution are needed?



Answer :

To make 21 gallons of 3% disinfectant solution, 7 gallons of 5% solution are used, and 14 gallons of 2% solution are used.

21 gallons of the 3% solution is required.

Therefore, the amount of disinfectant in the solution

= 3/100  X  21 gallons

= 0.63 gallons

Let the amount of 5% disinfectant solution used be x

Therefore,

the amount of 2% disinfectant solution used is (21 - x)

Now, the amount of disinfectant added through these solutions must be equal to the amount of disinfectant in the solution.

Hence,

5/100 X x  +  2/100 X (21 - x) =  0.63

or, 5x/100 + (42 - 2x) / 100 = 0.63

or, 0.05x + 0.42 - 0.02x = 0.63

or, 0.03x = 0.63 - 0.42

or, 0.03x = 0.21

or, x = 0.21 / 0.03

or, x = 7

Therefore 21 - x = 14

Hence 7 gallons of 5% solution is used and 14 gallons of 2% solution is used.

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