Algebra Chapter 3 section 9 Weighted Averages Algebra Chapter 3 section 9

Mixture Problems Yummy Cookie Company sells chocolate chip cookies for $6.95 per pound and white chocolate cookies for $5.95 per pound. How many pounds of chocolate chip cookies should be mixed with 4 pounds of white chocolate cookies to obtain a mixture that sells for $6.75 per pound.

c Fill in chart $6.95 $6.95c $5.95 $5.95(4) 4 c+4 $6.75 $6.75(c+4) # of pounds Price per pound Total price Fill in chart Chocolate chip c $6.95 $6.95c White Chocolate $5.95 $5.95(4) 4 Mixture c+4 $6.75 $6.75(c+4)

Set up your equation 6.95c + 5.95(4) = 6.75(c + 4) Use the last column to create an algebraic equation: 6.95c + 5.95(4) = 6.75(c + 4) 6.95c + 23.80 = 6.75c + 27 Now use your expert skills to solve for the variable … what do you get for w? c = 16, so 16 pounds of chocolate chip cookies need to be mixed with 4 pounds of white chocolate cookies

Try another one … Example #2: The Quik Mart has two kinds of nuts. Pecans sell for $1.55 per pound and walnuts sell for $1.95 per pound. How many pounds of walnuts must be added to 15 pounds of pecans to make a mixture that sells for $1.75 per pound?

Fill in chart 15 w w+15 Pecans Walnuts Mixture Price per pound # of pounds Total Price Pecans 15 $1.55 1.55(15) w Walnuts $1.95 1.95w w+15 Mixture $1.75 1.75(w+15)

Set up your equation 15(1.55) + 1.95w = 1.75(w + 15) Use the last column to create an algebraic equation: 15(1.55) + 1.95w = 1.75(w + 15) Again … use your expert skills to solve for the variable … what do you get for w? 23.25 + 1.95w = 1.75w + 26.25 w = 15, so 15 pounds of walnuts need to be mixed with 15 pounds of pecans to make the $1.75 per pound mixture

Mixtures with percents How many quarts of pure orange juice should Mike add to a 10% orange drink to create 6 quarts of a 40% orange juice mixture? Let p represent the number of quarts of pure orange juice he should add to the orange drink. Fill me in … % of solution Quarts Amt of juice p Orange juice 100% = 1 1p Orange drink 10%=0.1 6 - p 0.1(6 – p) Orange mixture 40%=0.4 6 0.4(6)

Set up your equation 1p + 0.1(6 – p) = 0.4(6) 1p + 0.6 – 0.1p = 2.4 Use the last column to create an algebraic equation: 1p + 0.1(6 – p) = 0.4(6) Again … use your skills to solve for p … 1p + 0.6 – 0.1p = 2.4 0.9p = 1.8  p = 2 qts So, 2 quarts of pure oj added to 4 qts of 10% oj will result in 6 qts of 40% oj

Rate Problems (d = rt) At 7:00 am, two groups of hikers begin 21 miles apart and head toward each other. The first group, hiking at an average rate of 1.5 miles per hour, carries tents, sleeping bags and cooking equipment. The second group, hiking at an average rate of 2 miles per hour, carries food and water. Let t represent the hiking time.

Create and fill in chart d = rt First group of hikers 1.5 t 1.5 t Second group of hikers 2 t 2 t 21 miles

1.5 t + 2 t = 21 Set up your equation Use the last column to create an algebraic equation: 1.5 t + 2 t = 21 Solve for t  3.5 t = 21 (divide both sides by 3.5) t = 6  what does that mean? The time it took for the two groups to meet took 6 hours. ? How far did the first group of hikers hike …?

Rate Problems (d = rt) Two city buses leave their station at the same time, one heading east and one heading west. The eastbound bus travels at 35 miles per hour, and the westbound bus travels at 45 miles per hour. In how many hours will they be 120 miles apart?

Create and fill in chart Eastbound Bus r t d = rt 35 t 35 t Westbound Bus 45 t 45 t 120 miles

35 t + 45 t = 120 Set up your equation Use the last column to create an algebraic equation: 35 t + 45 t = 120 Solve for t  80 t = 120 (divide both sides by 80) t = 1.5  what does that mean? The time it took for the two buses to be 120 miles apart took 1.5 hours. ? How far did the Eastbound bus travel …?

Espresso or Cappuccino? Suppose the Central Perk coffee Shop sells a cup of espresso for $2.00 and a cup of cappuccino for $2.50. On Friday Rachel sold 30 more cups of cappuccino than espresso , and she sold $178.50 worth of espresso and cappuccino. How many cups of each were sold? Fill me in …