In a school picnic, a total of 43 students brought a backpack, a lunchbox, or both a backpack and a lunchbo: If there are a total of 23 backpacks and 25 lunchboxes, how many students brought both a backpack and a lunchbox? 81200439 (A) 5 (B) 7 (C) 10 (D) 17 (E) 20 (ebasanud n alione1 to 15: 25 LT

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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**Problem Statement:**

In a school picnic, a total of 43 students brought a backpack, a lunchbox, or both a backpack and a lunchbox. If there are a total of 23 backpacks and 25 lunchboxes, how many students brought both a backpack and a lunchbox?

**Options:**

(A) 5  
(B) 7  
(C) 10  
(D) 17  
(E) 20  

**Solution Explanation:**

To solve this problem, we can use the principle of inclusion-exclusion. Let's define:

- \( B \) as the set of students who brought backpacks.
- \( L \) as the set of students who brought lunchboxes.

According to the information given:

- \(|B| + |L| = 43\) (total number of students who brought either or both)
- \(|B| = 23\) (students who brought backpacks)
- \(|L| = 25\) (students who brought lunchboxes)

We need to find \(|B \cap L|\), the number of students who brought both a backpack and a lunchbox.

Using the formula for inclusion-exclusion:
\[
|B| + |L| - |B \cap L| = 43
\]

Substitute the known values:
\[
23 + 25 - |B \cap L| = 43
\]

Solve for \(|B \cap L|\):
\[
48 - |B \cap L| = 43
\]

\[
|B \cap L| = 48 - 43 = 5
\]

Therefore, the number of students who brought both a backpack and a lunchbox is \( \boxed{5} \), which corresponds to option (A).
Transcribed Image Text:**Problem Statement:** In a school picnic, a total of 43 students brought a backpack, a lunchbox, or both a backpack and a lunchbox. If there are a total of 23 backpacks and 25 lunchboxes, how many students brought both a backpack and a lunchbox? **Options:** (A) 5 (B) 7 (C) 10 (D) 17 (E) 20 **Solution Explanation:** To solve this problem, we can use the principle of inclusion-exclusion. Let's define: - \( B \) as the set of students who brought backpacks. - \( L \) as the set of students who brought lunchboxes. According to the information given: - \(|B| + |L| = 43\) (total number of students who brought either or both) - \(|B| = 23\) (students who brought backpacks) - \(|L| = 25\) (students who brought lunchboxes) We need to find \(|B \cap L|\), the number of students who brought both a backpack and a lunchbox. Using the formula for inclusion-exclusion: \[ |B| + |L| - |B \cap L| = 43 \] Substitute the known values: \[ 23 + 25 - |B \cap L| = 43 \] Solve for \(|B \cap L|\): \[ 48 - |B \cap L| = 43 \] \[ |B \cap L| = 48 - 43 = 5 \] Therefore, the number of students who brought both a backpack and a lunchbox is \( \boxed{5} \), which corresponds to option (A).
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