Math Problem Statement
There are 45 students in a class. There are two times as many students with blond hair as with blue eyes. 8 students have blond hair and blue eyes, and 8 students are neither blond hair nor blue eyes. How many students have blue eyes?
Solution
Let's solve this problem step by step using the principle of inclusion-exclusion.
Definitions:
- Let represent the number of students with blond hair.
- Let represent the number of students with blue eyes.
- Let represent the number of students with both blond hair and blue eyes.
- Let represent the number of students with either blond hair or blue eyes or both.
Given:
- Total number of students: 45
- Number of students with both blond hair and blue eyes:
- Number of students with neither blond hair nor blue eyes: 8
- Number of students with blond hair is twice the number of students with blue eyes:
Step 1: Find the number of students with either blond hair or blue eyes
The number of students with neither blond hair nor blue eyes is 8, so:
Step 2: Use the inclusion-exclusion principle
The inclusion-exclusion principle states: Substitute the values:
Step 3: Substitute into the equation
Step 4: Check the values
- Number of students with neither: 45 - 37 = 8 (which matches the problem statement).
Conclusion:
The number of students with blue eyes is 15.
Would you like more details or have any questions? Here are 8 related questions that might interest you:
- How many students have blond hair but not blue eyes?
- What is the probability of selecting a student with both blond hair and blue eyes?
- How would the number change if there were 5 more students with blue eyes?
- How can we represent this problem using a Venn diagram?
- What if the ratio of blond hair to blue eyes were different?
- How many students have only blue eyes?
- What is the number of students with only blond hair?
- How would the equation change if 10 students were neither blond nor had blue eyes?
Tip: In problems involving ratios and sets, consider using the principle of inclusion-exclusion to avoid double counting.
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Math Problem Analysis
Mathematical Concepts
Sets
Inclusion-Exclusion Principle
Formulas
-
Theorems
Inclusion-Exclusion Principle
Suitable Grade Level
Grades 7-9
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