Ask Marilyn: Sharper Vision Or Not?

Steve Solomon of Huntingdon Valley, Pennsylvania, writes:

Marilyn: You gave a very clear and accurate explanation of 20/20 vision, ending with the statement, "The larger the fraction, the sharper the vision." (October 7, 2012) While this is certainly true, as a community college mathematics instructor, I can guarantee you that many readers will think that 20/100 is "larger" than 20/15. This kind of misconception is only the tip of the iceberg: You wouldn't believe how mathematically deficient many recent high school graduates are.

You could argue that they are not necessarily your readers so I might have to back off on my guarantee, but saying, "The smaller the bottom number, the sharper the vision," would have resulted in more people understanding your explanation.

Marilyn responds:

I'll consider your guarantee void, Steve—I just couldn't write what you said to my readers!