Multiplying Mixed Numbers

Directions: Using the digits 1 to 9 at most one time each, fill in the boxes to make the smallest (or largest) product.


How can we tell whether it would be better to put the larger numbers in the whole number, numerator, or denominator?


The current largest product was found by Sandy Pray’s student and is 8 7/1 * 9 6/2 = 180. It beats the former largest product of 9 7/1 * 8 6/2 which was found by Ivy Kong’s students.  The current best answer for smallest product 1 3/9 * 2 4/8

Source: Robert Kaplinsky

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  1. Hi Robert, my students figured out that the largest product is 9 7/1 * 8 6/2, which is 176. 🙂

  2. Our student discovered 8 7/1 * 9 6/2 = 180. Beats 176 by 4 points but even more made a very reserved student feel like queen of the day!

    • Wow. Thank you so much for sharing that Sandy! There are never enough moments to make students feel that way. I’ll update the answer.

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