• Purpose: To solve word problems involving mixtures.

• Homework: p. 322 – 325 1- 11 all. 13 – 21 odd.

Example # 1

• A grocer makes a natural breakfast cereal by mixing oat cereal costing $2 per kg with dried fruits costing $9 per kg. How many kg of each are needed to make 60 kg of cereal costing $3.75 per kg?

• Use a chart to organize the information.

• You have 2 types plus a mixture, so you need three rows.

Organized Chart

 # of Kg x

Price per

kg = Total Cost 

cereal   x 2  2x 

 fruits 60 - x  9  9(60 - x )

mixture 60   3.75  225

• Make your equation. (2x + 540 – 9x = 225)• Solve. – 7x = - 315 x = 45• Make sure you answer the question.• 45 kg of cereal and 15 kg of fruits is the answer.

Example #2

• How many liters of water must be added to 20L of a 24% acid solution to make a solution that is 8% acid?

• Organize into a Chart.• Water does not have acid, so it’s 0.

   # of L % Acid   Amt. of Acid

 acid  20  .24  .24(20)

 water x   0 0 

 mixture 20 + x  .08 .08(20 + x) 

Example #2 (cont.)

• Make your equation. The first mix plus water added is the total mixture.

• 4.8 + 0 = .08(20 + x) **Keep the decimals or multiply the equation by 100 to get rid of them.

• 100(4.8 + 0) = 100[.08(20 + x)]

• 480 = 8(20 + x) ; 480 = 160 + 8x

• 320 = 8x ; x = 40

• 40L of water must be added.

How many kg of water must be evaporated from 12 kg of a 5% salt solution to produce a

solution that is 30% salt?

• .05(12) + 0 = .30(12 - x) **Get rid of decimals.• 100(.05×12) = 100[.30(12 – x)]• 5(12) = 30(12 – x) ; 60 = 360 – 30x• -300 = -30x ; x = 10• 10 kg of water must be evaporated.

   Kg % Salt  Amt. Salt 

original  12   .05  .05(12)

 water  x  0  0x

new   12 - x  30 .30(12 – x)