Algebra Demystified 2nd Ed

270 algebra De mystif ieD

6. 0% 50% 40%

cups

+ 25 – x^

cups

=^25

cups

0 x + 0.50(25 – x) = 0.40(25)

00 50 25 04025

01 25 05 0100

12512

xx

x

+−=

+− =

−−

.( ).()

...

. ..
..
.
.

5

05025

25

050

5

−=−

=−

−

=

x

x

x

Mix 5 cups of decaffeinated coffee with 25 – x = 25 – 5 = 20 cups of 50%

caffeine coffee to produce 25 cups of 40% caffeine coffee.

7. 100% 35% 50%

x^

ounces

+^18

ounces

= x + 18^

ounces

1.00x + 0.35(18) = 0.50(x + 18)

1000 35 18 05018

10063050 9

050

..().( )

...

.

xx

xx

+=+

+= +

− xxx

x

x

x

−

+=

−−

=

=

050

0506390

63 63

05027

27

050

.

...

..

..

.

.

xx=54.

Add 5.4 ounces of pure acid to 18 ounces of 35% acid solution to pro-

duce a 50% acid solution.