A custodian is going to mix a 4% ammonia solution and a 12% ammonia solution to get 1 gallon (128 fluid ounces) of a 9% ammonia solution. How many fluid ounces of the 4% solution and the 12% solution should be used?

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Answer 1 · 2015-08-23T19:03:03

#48# ounces of 4% solution and #80# ounces of 12% solution will give #128# ounces of 9% solution.

Let the number of ounces of 4% solution be #k#
#rarr# the number of ounces of 12% solution must be #128-k#

#4k + 12(128-k) = 9(128)#

#4k + 1536 -12k = 1152#

#-8k = -384#

#k = 48#
#48# ounces of 4% solution and
#128-48 = 80# ounces of 12% solution