# 25 Funny Calculations That Are Interesting Yet Useless

Learning math seemed pretty useless after we learned addition and subtraction. Everything else was just extra. Show me where we have ever needed the logbook! I ask again, can anyone tell me, at what point in life am I going to need my logbook skills?

While math can at times seem illogical and useless, there are occasions however when it can prove quite entertaining. Scroll below for a collection of math memes that will have you racking your brain trying to remember some of those math lessons from long ago again just so you can puzzle out the answers to the interesting posts below.

More info: Reddit

## #1 One 9 Inch Pizza vs. Two 5 Inch Pizzas

Image source: GuvSingh

## #2 Approximately How Large Would The Car Have To Be In Order To Be That Curved?

Image source: CrazyPotato1535

“Quick eyeballing suggests a curvature of about 30°; that’s 1/12th of a full circle, so given that the Earth’s circumference is just over 40,000 km, the car would have to be about 3333 km long, or about the driving distance from Chicago to Los Angeles, or about 5.5 million washing machines (in case you’re too American to understand kilometers).”

## #3 How Many Rocks Would This Person Have To Throw To Flood Denmark?

Image source: stretch_armstrong_

“The total area of ocean is about 361 million square km, or 3.61 x 1014 square meters.

The highest point of Denmark is about 171m.

The earth is large enough that we can choose to ignore the curvature over a change of radius of 171m (compared to the radius of 6300km it’s less than a rounding error).

What we can’t ignore is that there is about 30 million square km of land that is 171m or less above sea level which will also be flooded (estimating from a hypsographic curve). I’ll factor in a mean of half of that to give the new earths surface figure of 3.76 x 1014 square meters.

This means that there would need to be 171 x 3.76 x 1014 = 6.43 x 1016 cubic meters of water displaced.

If we assume a good throwing rock has a volume of 1 litre, then you would need 6.43 x 1019 rocks.

At 1 rock per day that’s going to be 1.76 x 1017 years, or 12 900 000 times the age of the universe.

If all 8 billion people on the world threw one rock per second, it would only take 250 years”

## #4 What Are The Odds?

Image source: SMOKE1798

“Beginner: 1 in 102 million

Intermediate: 1 in 6.1 million

Expert: 1 in 477,000”

## #5 As It Asks, Which One Is The Better Deal?

Image source: Par4d0xxxx

“A circle has 360 degrees, so 60/360 is 1/6th of a pizza, and 45/360 is 1/8.

The area of a circle is (pi)r2

The area of the 6″ pizza is 1/6(pi)(62 )=6(pi)

The area of the 7″ pizza is 1/8(pi)(72 )=6.125(pi)

6.125/6=1.021, so the 7″ pizza is 2.1% bigger

$1.70/$1.50 is 1.13, or 13% more expensive.

The 7″ pizza is 13% more expensive, but only 2.1% bigger, so the 6″ pizza is a better deal.”

## #6 How Tall Would This Tree Have Been, And How Visible Would It Have Been?

Image source: BrightInsight6

“So the ave stump height is cut to 0.45 m. Let’s assume an oak, with an ave height of 20m. Thats about 2.3% of overall height.

This tree would therefore be around 11.7km high using that ratio. Almost high enough to tickle the stratosphere at 12km

So if I used the horizon calculator right, you could still see the bastard 387km away

EDIT: Just to answer a few of the many questions. In American that’d be about 7.3miles, or 13,760 washing machines”

## #7 How Much Does This Kitten Weigh?

Image source: g-amefreak

“One source says the “minimum actuation force” of a key is 47.6 grams. If we assume the kitten is standing on 4 keys (only one per paw) 4*47.6 is 190.4 grams or 0.4 pounds. Ao the kitten would be under that weight. It appears that the kitten is standing on more than 4 keys though so maybe 1/2 pound.”

## #8 What Is A Penguins Slapping Power?

Image source: CreativeName6574

“The average emperor penguin slaps with about the same force as a middleweight boxer. 800-1000 PSI”

## #9 A Lot Of Paper, But How Much

Image source: noideaman69

“36,567,729 sheets of letter sized paper according to Excel (single sided)

According to Google a pallet contains 200,000 sheets

Therefore 182 pallets of paper would be needed.

A photocopier can apparently print 500,000 sheets in its lifetime, so you would need 73 photocopiers”

## #10 How Much Would This Cost In That Time?

Image source: LeRealGabrielGD

“He’s a corporate executive of some sort and the trip was being paid for by the family member in Paris. His wife was also a fairly successful artist.

A 800k house in Bay Area probably cost >5M today”

## #11 A Natural Headache Cure

Image source: AlanPlotzker

## #12 How Many Combinations Of 9 Ingredients Are Possible. Using All 9 At Once Is Not Required

Image source: gracecamille_

“Each ingredient can either be included or not — that’s 2 possibilities. Multiply out all 9 ingredients and we have 29 = 512 in total. I presume you’d want to exclude the 1 possibility where none of the ingredients are included, so that leaves 511.”

## #13 I’ve Always Wondered How Much Money Walt Actually Had

Image source: Danny13oyy

“Assuming those are $100 bill stacks at $10,000 each. I count 12 stacks across and 15 stacks deep and assuming that each stack is ~0.5 inches tall with a total height of ~30 inches.

12 * 15 * (30 / 0.5) * 10,000 = $108 Million dollars.”

## #14 How Much Would This Cool The Tea?

Image source: CEO_Of_Rejection_99

“Oh come on this is doable from an engineering point of view:

One sip per second of 10ml (a shot glas’ equivalent in a few seconds)

90°C tea, 0°C water (I see ice?), ∆T =90

Conduction in the thin straw is negligible, basically water-to-water heat transfer at a slow rate: the convection coëfficiënt for that is about 1000W/m²K (forced convection water to unforced water essentially)

Straw is 5mm diameter, 150mm length is submerged. Total area = 5π*150 = 2350mm² heat exchange area.

As such, the heat (power) transferred per second is = 9010002350/1e6 ≈ 211W

211W for 0.01kg water (tea) per second is ∆T = 211/4200/0.01 ≠ 5°C difference.

This matches my experience: the straw is simply not big enough to offer proper area for heat exchange:

Source: 10 years of steam boiler engineering

Hope you enjoyed!”

## #15 How Much Force Is Superman’s Key Putting Down And Shouldn’t It Have Its Own Gravitational Pull?

Image source: Interesting_Judge863

“500,000 tons is its downward force due to gravity. It has a gravitational pull, but minimal compared to the earth (6,000,000,000,000,000,000,000 tons)”

## #16 What Does His Shirt Say

Image source: tabanopro

“The quote is “I’m sexy and I know it”

sqrt(1+tan^2) can be verbalized as “sec” and so this formula is the “sec of c”

“I’m sec C and I know it””

## #17 Really Though, How Much Different Exactly?

Image source: destructorrobot

“$9.33 on the left and $21.51 on the right”

## #18 How Many Nickels Would It Take To Crush You?

Image source: ropermarisa

“According to a google search, it takes about 4,000 newtons to crush a bone, & I’m going to assume that an average person has a frontal surface area of 1 m2 for ease.

A nickel weighs 5 grams, which equates to about 0.05 newtons of gravitational force… you’d need at least 81,578 nickels on top of the person, or about $4,078.90”

## #19 How Fast Would You Need To Go To Successfully Complete The Loop?

Image source: darthbane911

“Im gonna assume the loop is about 60m based on the height of the building next to it.

At the top of the circle, the two forces are mg and centripetal force. The two together equal ma (a being v2/r.) So mg + Fc = m(v2/r). Set Fc to 0 as you would have to have a centripetal force slightly above 0 to complete the loop. This gives us v2 = sqrt(gr). For a 60m loop (30m radius) v = 17.1m/s.

This is the speed at the TOP of the loop. Using conservation of energy, we can say that 1/2mv2 + mgh = 1/2mv2 (the first part is top of loop, second part is bottom of loop). Cancel m and plug in numbers.

You would have to travel 38.34m/s or 138kph (85.7mph) to make the loop.”

## #20 Is It True?

Image source: UberFacts

“If only contacting the floor with the heel then yes.

An elephant’s foot is 15-19 inches across, so assuming it’s vaguely circular gives an area of at least 0.114m2 per foot. Elephants when walking depending on the gait will have 2/3 feet in contact with the floor – so that’s at least 0.228m2 in contact with the floor. (Going for minimum area as this will give the highest pressure for the comparison)

6000lbs under Earth’s gravity is a force of 26.7kN, which when divided by area for a pressure of ~117kPa – if it’s just standing still this could actually be halved to approx 58kPa

If a 100lb woman (445N) is standing on only her heels (~1cm2 x 2) this is a pressure of 2,224kPa which is indeed about 20 times higher than the elephant on 2 feet.

However that’s not really representative of how heels are worn, even the picture shown has the shoes in contact with at least 20x the area of the ground than just the heels”

## #21 Is This True?

Image source: stem_feed

“They’re called crinkle crankles. A single leaf wall over that distance would need brick piers approx every 1.5-2m if it was a retaining wall it would need to be at least 9” wide (2 bricks). The crinkle crankle has more strength due to it’s curved nature so can be 4” wide or a single leaf of bricks.

For the maths if we can assume they’re true semi-circles then each semi circle would be 1/2piD or 1.57D whereas a double leaf wall would be 2D for the same length D

Therefore using 21.5% less bricks than a double leaf wall”

## #22 Is This True And If Yes How Deos It Work?

Image source: PleaseBeGneiss

“Quite the opposite, it will leave you with less sandwich. Since no cut is perfect, some of the sandwich molecules will stay on the knife or there is more crumbs on the cutting board. Therefore, cutting on a diagonal (longest cut) will dislodge more material of the sandwich than cutting along shorter line”

## #23 How Much Would This Actually Cost?

Image source: ElonsBeans

“Return flight JFK – Madrid: ~€750 Minimum income in Spain: €850/mo; 24 months amount to €20400. We’ll assume that since a lot of people in Spain have to make do with this much, you will figure it out too. Learning Spanish is pretty straightforward, if you live in Spain for 2 years, you’re practically guaranteed to pick up enough of it to get by, but let’s say you spend €100 on a couple textbooks and a dictionary, just to get you started. Depending on where in the US you live, there might even be a solid chance that you already speak the language, after all it’s the country’s second language, with more speakers in the US than in Spain. You will also be spending a bit on visas and other bureaucratic requirements, let’s call that another €200. Running with the bulls and getting trampled can be had for free. And then there’s the hip replacement itself, at $7,371, or €7074. However, depending how you play it, you could actually take a minimum-wage job in Spain, and qualify for public healthcare, in which case the hip replacement might actually be covered. But let’s just assume you have to pay for it out of pocket (which, frankly, is a pretty unusual thing in Europe, and typically only happens when people have to get treatement abroad and the insurance situation hasn’t been figured out, or for a couple religious weirdos who object against having health insurance on moral grounds).

So let’s ring you up; grand total: €28524, that’s about $29700.

Not only does it fit comfortably into the US figure, you even have some $12,000 to spare”

## #24 If The Sun Turned Into A Black Hole Of Equivalent Mass, Would The Accretion Disk Disk Be Large Enough To Destroy The Earth? If Not, How Bright Would It Be?

Image source: Valdevia_Art

“NASA did the math on this

“If the Sun was replaced with a black hole that had the same mass as the Sun, the Schwarzschild radius would be 3 km (compared to the Sun’s radius of nearly 700,000 km). Hence the Earth would have to get very close to get sucked into a black hole at the center of our Solar System.””

## #25 What Are The Actual Odds Of Winning 32 Hands Of Blackjack In A Row?

Image source: Mammoth_Hippo8930

“I believe blackjack gives the house a 0.61% edge over the player on average when played absolutely perfectly. Assuming the same odds for every game, .493932 leads me to a .000000000157% chance of winning 32 games in a row.”

## Got wisdom to pour?