Question 1102693
We want to know how many gal. at 15% to mix with 24%.
We need a total of 25 gal. at 18%

Using the method of alligation.
<pre>
24         3 1/3*25=8 1/3 gal of 24% solution
      18     8 1/3+16 2/3= 25.0 gal of 18% solution
15         6 2/3*25=16 2/3 gal of 15% solution
           9
</pre>
check
0.15 * 16 2/3 + 0.24 * 8 1/3 = 0.18*25
2.5 + 2.0 = 4.5
4.5 = 4.5
ok