## Can You Find the Error?

I used to be the editor of the “Media Clips” column in the Mathematics Teacher journal. One objective of the column was to identify the use of incorrect mathematics in print. The following flyer from H. H. Gregg would have been a great example.

My favorite entry in the “Media Clips” column was a clip from the Salt Lake Tribune on October 11, 2002, which read:

A Salt Lake County Health Department inspector paid a visit recently [to the Coffee Garden restaurant] and pointed out that research by the Food and Drug Administration indicates that one in four eggs carries salmonella bacterium, so restaurants should never use more than three eggs when preparing quiche. [The Coffee Garden’s quiche recipe calls for four fresh eggs.]

Priceless.

Anyway, back to H. H. Gregg. The image above may be too small or blurry to identify the error, so here’s an enlargement.

I gave the flyer to my sons and told them that they could have ice cream for dessert if they were able to identify the math error. I’ll make the same offer to you — first person to post the error to the comments gets an ice cream cone from me.

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• 1. Chris  |  June 17, 2013 at 2:01 am

They’ve made the common mistake of assuming time is measured in decimal form. It’s really 13hrs each day and 13×3=39.
Make mine vanilla 🙂

• 2. venneblock  |  June 19, 2013 at 10:59 pm

• 3. Chris  |  June 20, 2013 at 2:05 am

Patrick,
Thanks very much…of course the voucher’s no use to me here in Scotland so if you email me I’ll forward on the voucher so Alex and Eli can enjoy an ice cream treat 🙂
Chris

• 4. Chandrashekara K A  |  June 17, 2013 at 2:38 am

13-15, 9a-10p is more than 2 days(48+13 = 61 hrs). They probably meant 13-14 June.

• 5. venneblock  |  June 19, 2013 at 10:50 pm

Hadn’t considered that possibility, but 9am on June 13 until 10pm on June 14 is 37 hours, not 33.

• 6. Roger Armstrong  |  June 17, 2013 at 3:03 am

9a – 10p is 13 hours. 13 hours over 3 days is 39 hours, not 33.

• 7. James  |  June 17, 2013 at 3:36 am

Their wall clock obviously stops at 10.

The error is that three days for 13 hours a day should be 39 hours, not the advertised 33.

• 8. puntomaupunto  |  June 17, 2013 at 3:53 am

in base 12 the total number of opening hours is correct. And time *is* computed in base 12, isn’t it?

• 9. zachdcox  |  June 17, 2013 at 9:56 am

I think if time were computed in base 12 the the hours would be 1,2,3,4,5,6,7,8,9,A,B,10 … I think the time is computed modulo 12 vs base 12.

• 10. Albert  |  June 17, 2013 at 6:48 am

should be 39 hours

• 11. Gerard Blais  |  June 17, 2013 at 9:10 am

61 hours?

• 12. zachdcox  |  June 17, 2013 at 9:54 am

9 am to 9 pm is a span of 12 hours — 9 am to 10 pm is a span of 13 hours. So the final 33 hours (June 13,14,15) should be computed from 9 am to 8 pm which is a span of 11 hours (11*3 = 33 vs 13*3 = 39)

• 13. xander  |  June 18, 2013 at 10:54 am

Obviously, the date is given by a subtraction in the positive integers (or, perhaps as suggested above, modulo 30, as June has 30 days). Since 13-15=-2, the date is either 28 June, giving a 13 hour sale, or -2 June which seems to correspond to 29 May (31 May = 0 June ?), again giving a 13 hour sale. In either case, 33 hours is definitely wrong.

You can get me my ice cream next time you are in Reno. 😛

• 14. venneblock  |  June 19, 2013 at 11:05 pm

Your response is dizzying, Xander. Next time I’m in Reno, I’ll buy you a cone and myself a beer… especially if you start talking like this.

• 15. lwit  |  June 19, 2013 at 5:43 pm

Clearly it should be a colon, not a semi-colon! Also, it could be 9am on June 13 to 10pm on June 15, which is 61 hours! But I wouldn’t want to work those shifts.

• 16. Pravin shah  |  November 7, 2013 at 6:38 pm

Talking from experience H H Greg salesmen and women are NOT hired based on their I Q. One salesman told me the new computer would used 110% less power than the older model…..

I asked him, if I put a full cup of coffee, on it, while the power was off, would it warm up my coffee ?? 110% less power usage! means that it actually generates it’s own power….. You cannot have anything like more than a 100 % less …..

The Math Jokes 4 Mathy Folks blog is an online extension to the book Math Jokes 4 Mathy Folks. The blog contains jokes submitted by readers, new jokes discovered by the author, details about speaking appearances and workshops, and other random bits of information that might be interesting to the strange folks who like math jokes.

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