Brain Teaser: Who Can Creep Under the Wire Around the Earth?

Put on your thinking caps and solve this brain teaser.


The circumference of the Earth is around 40,075 km.

If we made a circle of a wire around the globe, that is only 10 meters (0.01 km) longer than the circumference of the globe;

Who among the following (an ant, a mouse, or a man) could be able to creep under it?

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Answer: All can Creep under the wire.

Explanation:

Rather than doing complex calculations, it is easier to compare the old and new perimeter.

Let us consider the following;

R = Radius of Earth.


Rn = Radius of circle formed by the wire.

So basically we want to find the difference between the radius to see how much space is available for anyone to creep under it.

As per given information, let’s put them in equations.

Perimeter is 2πR,

Length of wire is 10 m more than earth’s circumference.

Earth’s circumference is 2πR = C1

Circumference of wire 2πRn =  C2

The difference between the 2 circumference is 10.

C2 – C1 = 2πRn – 2πR = 10

2π(Rn – R) = 10;

Rn – R = 10/2π = 5/(22/7) = 35/22 = 1.6m

So the difference between the circumference is 1.6 m which is also equal to 5’2”

So a short man can easily walk under it and a taller man would have to duck slightly to get past the wire.

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