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?