Modeling with Matrices Answers

Jacy has a collection of 140 coins worth $19.00. She has only nickels, dimes, and quarters. The difference in the number of dimes and the number of quarters is 10. Using matrices, how many nickels are in Jacy’s collection?

The compositions of three powdered drink mixes are shown in the table below. Drink Mix Composition Mix AMix BMix CCitric Acid0.100.150.20Flavoring0.100.050.10Sugar0.800.800.70Xavier needs to create 100 grams of a drink mix containing 18% citric acid, 8% flavoring, and 74% sugar. How much of Mix C should he use?

Indira has 18 coins valued at $4.20. She has only quarters and dimes. Which augmented matrix can be used to determine the number of quarters and dimes in the collection?

Elise, Maggie, and Francesca work for an insurance company making follow-up calls to clients. Each person works at a different rate. The table below shows the number of hours each person works over three days and the total number of calls that are made. Hours Worked and Total Calls Made EliseMaggieFrancescaTotal CallsMonday778247Tuesday659218Wednesday931156Elise makes the same number of calls every hour, Maggie makes the same number of calls every hour, and Francesca makes the same number of calls every hour. If Elise earns $1.50 per phone call, how much money does Elise make over the 3 days?

Jeremy’s fruit stand sells peaches and watermelons. In the first hour the fruit stand is open, 12 bushels of peaches and 5 watermelons are sold for a total of $150. In the second hour, 15 bushels of peaches and 8 watermelons are sold for a total of $198. A bushel of peaches costs p dollars, and a watermelon costs w dollars. Which matrix equation represents the situation?

An office building has three air conditioning units, one for each office. Each unit runs only when employees are working. The tables below show the number of hours employees worked at each office over a three-month period and the total air conditioning electric costs for the entire office for each month. Number of Hours Worked Unit AUnit BUnit CJune184207276July174198264August168189242Total Air Conditioning Electric CostsJune$142.60July$135.96August$128.30How much does it cost to run Unit A per hour?

A trail mix is made up of peanuts that cost p dollars per pound and dried fruit that costs d dollars per pound. A blend of pound of peanuts and pound of dried fruit costs $6.50. A blend of pound of peanuts and pound of dried fruit costs $4.50. Which matrix equation can be used to solve for the cost of 1 pound of peanuts and the cost of 1 pound of dried fruit?

A chemist has a container of 12% peroxide solution and a container of 20% peroxide solution. She needs to mix the two solutions to create 100 mL of a 14% solution. If x represents the amount of 12% peroxide solution and y represents the amount of 20% peroxide solution she needs, which matrix equation can determine the amount of each solution she needs to make the 14% solution?

For a client, a landscaper purchases 3 oak trees and 4 maple trees for $380. For his own home, the landscaper purchases 2 oak trees and 5 maple trees for $370. Which augmented matrix represents the situation?

A carnival charges each person an admission fee and a fee per ride. A family pays 6 admission fees, and they pay for a total of 20 rides. A couple pays 2 admission fees, and they pay for a total of 18 rides. The family pays a total of $64. The couple pays a total of $44. Which augmented matrix can be used to determine the cost per admission and the cost per ride?