A laboratory technician needs to make a
81-liter batch of a 20% acid solution. How can
the laboratory technician combine a batch of
an acid solution that is pure acid with another
that is 10% to get the desired concentration?

again i didnt answer the question i just found someone who did

hope it helps :)

Step-by-step explanation:

Let +a+ = liters of pure acid needed

Let +b+ = liters of 10% solution needed

+.1b+ = liters of pure acid in 10% solution

(1) +a+%2B+b+=+135+

(2) +%28+a+%2B.1b+%29+%2F+135+=+.2+

(2) +a+%2B+.1b+=+27+

(2) +10a+%2B+b+=+270+

Subtract (1) from (2)

(2) +10a+%2B+b+=+270+

(1) +-a+-+b+=+-135+

+9a+=+135+

+a+=+15+

and

(1) +a+%2B+b+=+135+

(1) +15+%2B+b+=+135+

(1) +b+=+120+

15 liters of pure acid are needed

120 liters of 10% solution are needed

check:

(2) +%28+a+%2B.1b+%29+%2F+135+=+.2+

(2) +%28+15+%2B.1%2A120+%29+%2F+135+=+.2+

(2) +27%2F135+=+.2+

(2) +27+=+27+

the circle one