Algebra Demystified 2nd Ed

Chapter 8 linear appliCaTionS 269

4. 65% 25% 40%

ml

+ 180 – x^

ml

=^180

ml

0.65x + 0.25(180 – x) = 0.40(180)

0650 25 180 04 0 180

06545025 72

04

..().( )

..

.

xx

xx

+−=

+− =

004572

45 45

04027

27

040

675

x

x

x

x

+=

−−

=

=

=

.

.

.

Add 67.5 ml of 65% acid solution to 180 – x = 180 – 67.5 = 112.5 ml of
25% solution to produce 180 ml of 40% acid solution.

5. 0% 45% 30%

liters

+^10

liters

= x + 10^

liters

0 x + 0.45(10) = 0.30(x + 10)

00 45 10 03010

045030 3

30 3

15 0

xx

x

+=+

+= +

−−

=

.().()

..

.

.. 330

15

030

5

x

x

x

.

.

=

=

Add 5 liters of water to 10 liters of 45% alcohol solution to produce a
30% alcohol solution.