Beginning Algebra, 11th Edition

SECTION 2.7 Further Applications of Linear Equations^147

17.In a chemistry class, 12 L of a 12% alco-

hol solution must be mixed with a 20%

solution to get a 14% solution. How many

liters of the 20% solution are needed?

18.How many liters of a 10% alcohol solu-

tion must be mixed with 40 L of a 50%

solution to get a 40% solution?

19.Minoxidil is a drug that has recently

proven to be effective in treating male pat-

tern baldness. Water must be added to

20 mL of a 4% minoxidil solution to dilute

it to a 2% solution. How many milliliters

of water should be used? (Hint:Water is

0% minoxidil.)

20.A pharmacist wishes to mix a solution that is 2% minoxidil. She has on hand 50 mL of a

1% solution, and she wishes to add some 4% solution to it to obtain the desired 2% so-

lution. How much 4% solution should she add?

21.How many liters of a 60% acid solution must be mixed with a 75% acid solution to get

20 L of a 72% solution?

22.How many gallons of a 12% indicator solution must be mixed with a 20% indicator

solution to get 10 gal of a 14% solution?

Work each investment problem using simple interest. See Example 3.

23.Arlene Frank is saving money for her college education. She deposited some money in a

savings account paying 5% and $1200 less than that amount in a second account paying

4%. The two accounts produced a total of $141 interest in 1 yr. How much did she invest

at each rate?

24.Margaret Fennell won a prize for her work. She invested part of the money in a certificate

of deposit at 4% and $3000 more than that amount in a bond paying 6%. Her annual

interest income was $780. How much did Margaret invest at each rate?

25.An artist invests in a tax-free bond paying 6%, and $6000 more than three times as much

in mutual funds paying 5%. Her total annual interest income from the investments is

$825. How much does she invest at each rate?

26.With income earned by selling the rights to his life story, an actor invests some of the

money at 3% and $30,000 more than twice as much at 4%. The total annual interest

earned from the investments is $5600. How much is invested at each rate?

15.A pharmacist has 20 L of a 10% drug

solution. How many liters of 5% solu-

tion must be added to get a mixture that

is 8%?

16.A certain metal is 20% tin. How many

kilograms of this metal must be mixed

with 80 kg of a metal that is 70% tin to

get a metal that is 50% tin?

Liters of Liters of

Solution Rate Pure Drug

20 20

0.05

0.08

1 0.10 2

Kilograms Kilograms

of Metal Rate of Pure Tin

x 0.20

0.70

0.50