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Chapter 7: Identify Subproblems. A mixture is 25% red paint, 30% yellow paint, and 45% water. If 4 quarts of red paint are added to 20 quarts of the mixture, what is the percentage of red paint in the new mixture?. Ask questions: What do you need to know?.
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Chapter 7: Identify Subproblems
A mixture is 25% red paint, 30% yellow paint, and 45% water. If 4 quarts of red paint are added to 20 quarts of the mixture, what is the percentage of red paint in the new mixture?
Ask questions: What do you need to know? How many quarts of red paint are in the new mixture? How many quarts of paint are in the new mixture? What percentage of the new mixture is red paint?
Ask questions: What do you need to know to answer these questions? How many quarts of red paint are in the new mixture? How many quarts of red paint are in the original mixture? And how many quarts of paint are in the original mixture?
Rearrange the list in an order that the questions can be answered. How many quarts of paint are in the original mixture? How many quarts of red paint are in the original mixture? How many quarts of red paint are in the new mixture? How many quarts of paint are in the new mixture? What percentage of the new mixture is red paint?
Solve the subproblems in order. How many quarts of paint are in the original mixture? How many quarts of red paint are in the original mixture? How many quarts of red paint are in the new mixture? 20 (given) 25% of 20 = 5 quarts 5 + 4 = 9 quarts
Keep solving. How many quarts of paint are in the new mixture? What percentage of the new mixture is red paint? 20 + 4 = 24 quarts 9 / 24 = 0.375 = 37.5%
Strategy: Identify subproblems • Ask questions: What do you need to know? • Ask more questions: What do you need to know to answer the first questions? • Stop when you have questions you can answer. • Rearrange the list in an order that the questions can be answered. • Solve the subproblems in order.