The volume of a aquarium is 231 cubic inches
10 × -2 is -20
-20 -8 = -28
72 % of 300 is 216
Divide 216 ( # of boxes unloaded ) by 30 (minutes they were unloading)
216 / 30 = 7.2
They unloaded 7.2 boxes each minute.
**DOUBLE CHECK:
Multiply 7.2 by 30
7.2*30 = 216
Answer : 7.2 boxes/minute
Total = 36oz
Amount of 18% solution = x
Amount of 9% solution = 36 - x
Using the fact that (amount of solution) * (percent HCl) = amount HCl we can set up an expression for the amount HCl in a mixture of 18% and 9% solutions with a total volume of 36oz.
Amount of HCl = x*0.18 + (36 - x)*0.09
If we divide this by the amount of solution we get percent HCl, and we have a target of 10% HCl. Now we have an equation to solve,
[x*0.18 + (36 - x)*0.09]/36 = 0.1
x*0.09 + 3.24 = 3.6
.09x = 0.36
x = 4
Therefore,
4 ounces of 18% HCl solution and 32 ounces of 9% HCl solution
Check:
[(4*.18) + (.09*32)]/36 = 0.1?
0.1 = 0.1 Yes.
-18x-17=-53 /add 17 to both sides
-18x-17+17=-53+17
-18x=-36
x=(-36)/(-18)
x=2
