A customer is buying two small boxes, totaling $2.14 with tax. She has a discount card, so I apply that, as well, bringing her total down to $1.84.

Customer: “How much did my discount save me?”

Me: “It looks like it saved you thirty cents.”

Customer: “But what did it save me?”

Me: “It saved you 15% off the boxes, today.”

Customer: “So if I bought more, my total would have been less?”

Me: *Pauses* “No.”

Customer: “Yes!”

Me: “Okay, how?”

Customer: “Because 15% off three, or even four, boxes is more than 15% off only two boxes.”

She gives me a smug look.

Me: “That’s… That’s not how that works. It seems like more of a discount, but only because the dollar amount is also higher.”

Customer: “No! I need four boxes.”

Me: “Okay. With the discount, that’s going to be $3.68.”

Customer: “Wait, no. Why is it more?”

Me: “Because you’re buying more boxes, so you’re spending more money.”

Customer: “Fine. Then I only want two boxes. You just lost a four-box sale!”

Related:
Math Is Your Friend, Part 7
Math Is Your Friend, Part 6
Math Is Your Friend, Part 5
Math Is Your Friend, Part 4
Math Is Your Friend, Part 3

My teenage son is idly playing with a length of rope.

Son: “I have a string! I can make scientific theory!”

Me: “Well, can you untie the knot in it before you theorize it into permanence?”

Son: *Play-threateningly* “Are you trying to stop scientific theory?! Do you know what we do to people who get in the way of science?!“

Me: “Canonize them?”

We have a live chat message come through from America with the following question.

Customer: “Hi, I’m a size thirty-six-inch waist… but that’s US size. Can you tell me what size in English inches I need?”

Related:
A Stupid Call By Any Metric, Part 2
A Stupid Call By Any Metric

I was a very precocious kid but didn’t have as much common sense to back it up. I taught myself how to read at two, and by three, I had learned enough math to be able to work the cash register at my grandpa’s small exotic pet store at the flea market. The entire family was required to help out during the weekend, though my “helping” was them indulging a small child until my attention span ran out and I wandered off.

We sold little feeder goldfish, three for $1, and they had always been bought in sets of three whenever I rang them up before. Someone came to the register with just a single tiny goldfish in a bag, leading to several seconds of confusion. Then, I yelled across the store in a slight panic.

Me: “[Grandpa]! How do you do one-third of a penny?!”

The customer and my grandpa both burst out laughing, and Grandpa called back to charge thirty-five cents.

Customer: “The sign says these books are three for $10, but the price stickers say $3.33 each. Which is it?”

Related:
Math Is Your Friend, Part 6
Math Is Your Friend, Part 5
Math Is Your Friend, Part 4
Math Is Your Friend, Part 3
Math Is Your Friend, Part 2