Question 911585
We need a total of 90 mL at 20%
We want to know how many mL at 4% to mix with 40%
a+b=90,
0.04*a+0.4*b=0.2*90
a=90-b
0.04*(90-b)+0.4*b=18
3.6-0.04b+0.4*b=18
0.36*b=14.4
b=40
a=90-b
a=50 mL at 4%
b=40 mL at 40%
check
0.04*50+0.4*40=0.2*90
2+16=18
18=18
ok
codemx1