21. Mrs. Fisher has 91 watches on display at her store. She says she can arrange them into rows and columns without any watches left over. Mr. Fisher says she can only make 1 row with all 91 watches. Who is correct? Explain.

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UpStudy AI · Accepted Answer

Mrs. Fisher is correct.

**Explanation:**

The statement revolves around whether the number **91** is a **prime number** or not.

1. **Prime Number Check:**
   - A **prime number** is a number greater than 1 that has no positive divisors other than 1 and itself.
   - To determine if 91 is prime, we can check for divisors other than 1 and 91.
   - **91 ÷ 7 = 13**, which means 91 can be expressed as **7 × 13**.

2. **Arranging Watches:**
   - Since 91 can be factored into **7 rows and 13 columns**, Mrs. Fisher can arrange the watches in a **7×13** grid without any watches left over.
   - This contradicts Mr. Fisher's claim that the only arrangement is one row of 91 watches.

**Conclusion:**
- **Mrs. Fisher** can indeed arrange the 91 watches into multiple rows and columns (specifically 7 rows of 13 watches each), proving that 91 is **not a prime number**.
- **Mr. Fisher** is incorrect in his assertion that only one row is possible.

**Therefore, Mrs. Fisher is correct.**
Mrs. Fisher is correct because 91 can be arranged into 7 rows of 13 watches each, which means it's not a prime number.

Mrs. Fisher has 91 watches on display
at her store. She says she can arrange
them into rows and columns without any
watches left over. Mr. Fisher says she can
only make 1 row with all 91 watches. Who
is correct? Explain.

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