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World-famous engineer John Johnson decided to take a break from his latest invention, and asked his wife if she had any chores he could do to clear his mind. She handed him a grocery list and told him to go to the store. The list contained perfectly ordinary items such as bread and yogurt, as well as batteries.

When John got home, his wife was surprised and perplexed to see that he had purchased a total of 170 batteries.

"Why did you buy so many batteries?" she asked.

John answered "I just bought the number on the list."

Perplexed, she looked at the list just to make sure and told him "I didn't even put a number here at all."

Why did John buy so many batteries?

Deusovi
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Devsman
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    This would make a bit more sense if JJ were a world-famous software or computer engineer, as other types of engineering have much less use for the important facts of this question. – Todd Wilcox May 02 '16 at 17:39
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    Because his kids keep taking them out of the remote –  May 02 '16 at 21:37
  • John Johnson should be Jon Skeet :P – palsch Jun 11 '16 at 06:26

2 Answers2

63

He did this because

170 in hex is AA. She asked for "Double A" batteries.

clintperry
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  • I thought it seemed a little on the easy side. Good job though. – Devsman May 02 '16 at 12:55
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    at least she didn't ask for the next size down... – ratchet freak May 02 '16 at 14:09
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    Wait, did she write 0xAA batteries? Otherwise it stretches the suspension of disbelief. – vsz May 02 '16 at 15:40
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    AA implies at least base 11 (since the standard decimal digits suffice for bases 2-10). Base 16 is arguably the most commonly used base that requires additional symbols for transcription. – Nathan Osman May 02 '16 at 16:38
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    The question remains - what size batteries did he buy? Since she didn't specify (at least by his interpretation), it's quite likely they're all the wrong type... – Darrel Hoffman May 02 '16 at 18:11
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    @DarrelHoffman Car batteries. – Devsman May 02 '16 at 18:23
  • @vsz no, because then he would have bought 0 batteries of the AA type. "Where are the batteries?" "I bought as many as you asked for!" – Buttle Butkus May 02 '16 at 20:23
  • This answer is incorrect. She did not ask for "double A batteries." She asked for "AA batteries," which can be interpreted as "170 batteries" in hexadecimal. I was going to leave this comment originally but was not allowed to yet ( not enough rep I guess), which is why I posted an answer instead. – Buttle Butkus May 02 '16 at 21:12
  • @ButtleButkus IMO, putting "Double A" in quotes (note that "batteries" is not included) implies it's a literal pronunciation of the term within the quotes, not a precise notation of the information. I think it's correct as-is. – thanby May 02 '16 at 21:16
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    Why did John buy so many batteries? Because his wife wrote "AA batteries" on her grocery list, which can be interpreted as "170 batteries" in hexadecimal. As a side note, "AA batteries" can be pronounced as "double A batteries" or as "A A batteries". As another aside, John could have saved a lot of money if he had interpreted "AA" as base 11 and bought 121 batteries. Or saved even more if he had just bought a few "double A batteries." – Buttle Butkus May 02 '16 at 21:46
  • As was stated above, my answer indicates pronunciation, not the literal note – clintperry May 03 '16 at 12:51
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The list said

"While you are at the store, if they have batteries, buy a pack." He looped until he bought the store's entire stock of 170.

Byron
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    Like the old one about the computer programmer who was found dead in his shower with hundreds of empty shampoo bottles - "Lather; rinse; repeat" – RDFozz Apr 23 '18 at 21:09