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 
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 
to be 
. So we have:
[Unparseable or potentially dangerous latex formula. Error 5 : 656x54]
So the answer is clearly 
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!
November 17th, 2005 at 12:27 pm
Doesn’t he know that math professors can’t be bothered with such simple computation. You have people who do your computation for you….. right?
November 17th, 2005 at 4:58 pm
I hope you called him back……Tell him you were just testing him.
If you never make mistakes, you’re not doing anything!
November 17th, 2005 at 5:02 pm
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.
November 17th, 2005 at 8:21 pm
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.
November 18th, 2005 at 12:43 pm
I’m planning on calling you with all my math questions from now on!
Be Forewarned!!
December 6th, 2005 at 4:14 pm
[…] The title of this blog seems to imply that this is the second in a series of blogging my mathematical blunders and in a way it is. The first blunder went untitled as such and I am almost afraid to bring attention to it again but was placed in the entry, “I should be fired!”. As I have pondered the content of this blog, I have decided that Monday is Blunder Day. (Yeah, I know it’s Tuesday, but I was sick yesterday, boohoo). It just seems appropriate that the hardest day to get through with out making dumb mistakes at the board should be a day honored by blogging about the careless errors I have made over the last week. The hope is that by doing so, I identify where my tend to make most of my mistakes and rectify that problem. I had in mind the blogging of some great ones, but realized that most of the mistakes I make are rather uninteresting. So, lucky for you, I decided to blog them anyway. […]