Cubic Confusion

(It’s no secret in my family that I’m very good at mental arithmetic. As a result, I’m frequently used to calculate any number of things going on in their lives under the pretense of “save me from finding the calculator.” Usually, it’s just a minor inconvenience in my day. Then, my dad says the magic words.)

Dad: “So, it measures 7 feet, by 7 feet, by 4 inches. How many cubic feet is that?”

Me: “16 1/3.”

Dad: “No! That’s too small!”

Me: “You said 7 feet, by 7 feet, by 4 inches, right?”

Dad: “Right.”

Me: “And there’s 12 inches to a foot, right?”

Dad: “Right.”

Me: “So, 4 inches is equal to 1/3 of a foot, right?”

Dad: “Right.”

Me: “So, 7, times 7, times 1/3. That’s 16 1/3.”

Dad: “No! You have to convert it to cubic inches first!”

Me: “Really?! You’re making me do it that way?”

Dad: “Yes, that’s how you do it.”

(Groaning and shaking my head, I do this considerably longer calculation.)

Me: “That’s 28,224 cubic inches, so… 16 1/3 cubic feet. Again.”

Dad: “What?! How did you turn 28,000 into 16?!”

(I grab a pencil and paper and walk him through every step of my work. We arrive at 28,224 just fine, and then we get to converting.)

Me: “So now we divide by 1728.”

Dad: “No! There are only 12 inches to a foot!”

Me: “It’s a CUBIC foot, Dad. That’s a cube measuring 12 inches, by 12 inches, by 12 inches. That’s 1728 cubic inches to the cubic foot. Or are you going to tell me that you think the answer is 2352 cubic feet?”

Dad: “You did something wrong!”

(He storms off, right towards the calculator. Meanwhile, I’ve pulled out my phone and found a source that proves there are 1728 cubic inches to a cubic foot, just in case I still need it, which I do. By the end of this encore of a needless conversion, we have, once again, arrived at 16 1/3.)

Dad: “THAT CAN’T BE RIGHT!”

Me: “Why don’t you show me what I’m calculating?”

(He leads me to the backyard and shows me a big, rectangular hole.)

Dad: “This is for the shed. I dug it out, and I just need to smooth it out. Tomorrow, I’m going to fill it. I need to know if I’ve got enough bags of cement. If it’s 16 1/3, I’d only need one bag, but I’m definitely going to need more like 30.”

(I see one of the bags he has out, and I start reading it to make sure all of his numbers are right. The bag says it’s good for 20 cubic feet of concrete, so by all outward appearances, my math is sound. Then, as I ponder why my dad insists he’s going to need 30, the gears in my head start winding.)

Me: “Dad, you are going to use concrete, right?”

Dad: “Yes!”

Me: *realizing how poorly I phrased my previous question* “Walk me through it. You empty this bag into the… whatever, and then?”

Dad: “Then I add the water until it’s the right consistency.”

Me: “That’s it?”

Dad: “Well, then I pour it, smooth it out, and build the shed.”

Me: *facepalming* “Oh, my God.”

Dad: “What?”

Me: “You don’t know the difference between cement and concrete, and you’ve done work on this house.”

(At least now we knew what the problem was. Now to figure out how many of his fixes around the house have to be redone.)