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.

Mrs. Fisher is correct because 91 can be factored into more than just one row. In fact, 91 can be arranged into multiple configurations, such as 7 rows of 13 watches each or 13 rows of 7 watches each. This means she has various options for organizing her watches. Mr. Fisher’s assertion that there is only one arrangement overlooks the concept of factors. When discussing arrangements in rows and columns, we need to consider all the pairs of numbers that multiply together to yield 91, not just the singular row where all watches are in one line. So, Mrs. Fisher has the upper hand on this one!