I should be fired!

So, the rest of my day is now shot. For the rest of the day, I will do nothing but think about a mistake I made this morning. Here’s the story:

Background: I love it when people come to me with questions, especially if it is from someone besides my students, like a friend in town or maybe even a complete stranger with a math question. I don’t get many of these calls, but when I do, I am very pleased to help.

This morning a man in my church called and said that he had a math question for me. There is a butcher in town that has 30 lbs of beef trat is 93% lean and wants to add fat to make it 90% lean. How much fat should he add. He was also kind enough to tell me that he had already called the Division chair in the Business department to get an anwer. I was witty enough reply, “So you want to double check his answer?” To which he replied, “Or yours.” At that moment in the conversation, a person came into my office so I had to call this man back.

As soon as I was done, I made the following calculations:

Let [tex]x[/tex] be the amount of fat to be added. Then, 30 lbs of fat at 93% lean means there is 93% lean beef, or 27.9 lbs, and 7% fat, or 2.1 lbs. Thus we need 10% of [tex] 30 + x[/tex] to be [tex]2.1 + x[/tex]. So we have:

[tex]begin{array} {rcl}0.1(30+x) & = &2.1+x
Rightarrow 3.0 + 0.1x &=& 2.1 + x
Rightarrow 1.8 &= &0.9 x mbox{Notice there is a mistake on this line}
Rightarrow x &=&2end{array}[/tex]

So the answer is clearly [tex]2.0[/tex] lbs. of fat. WRONG. Only I discover that I am wrong after I’ve called him back. The correct answer, which by the way, the Business Prof. was able to get is 1 lb. fat. Clearly on line two above, if you subtrack 2.1 from 3.0 you do NOT get 1.8 but 0.9. Dadgummit! Am I dyslexic or what? I don’t how I let that get by and now I have demonstrated incompetence in a simple area of algebra. ARGH!

What a day!

6 thoughts on “I should be fired!

  1. I’ve had those days … only they usually don’t involve math problems, but something along the lines of misspelled names or faulty facts that find their way into the newspaper. People have asked me why I feel so terribly sick after making a mistake. It is then that I point out that when I make mistakes 20,000 people are likely to know about it.

    By the way, I started reading your sermon but didn’t have time to finish it. I hope you had a good day.

    Like

  2. I guess that is a good thing that I only made a fool of myself in front of one person and not 20,000. Is it wrong to take pleasure in jonboy’s misfortunes?

    Thanks to Mom, too. I know you’re right. Plus, I’ll be even more careful to double and triple check my work in the future, remembering the fool I once made of myself.

    Like

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