# 10 most difficult geometry riddles

A list of geometry related questions that are most often answered incorrectly

Mathematics quiz
## What is the maximum distance a plane can fly travelling constantly North?

20,004 km. Continous travel North must eventually end at the North Pole. So, the maximum distance is half of the Earth's meridional circumference, which can be reached if a plane starts at the South Pole.

hard

41%

10,002 km

10,002 km

9%

20,004 km

20,004 km

41%

40,007 km

40,007 km

17%

It can fly endlessly (as long it can)

It can fly endlessly (as long it can)

31%

Created by: globalquiz.org.
Statistics based on 14822 answers in 2 languages
»

## If Earth's radius was larger by 1 meter, how much longer would its equator be?

By approx 6 meters. For each circle, the length of the circumference is c=2πr. Hence, if a radius grows by 1 meter, the circumference grows by 2 π meters - no matter what the initial value of radius was.

hard

45%

by approx 6 meters

by approx 6 meters

45%

by approx 6 kilometers

by approx 6 kilometers

18%

by approx 60 kilometers

by approx 60 kilometers

21%

by approx 6000 kilometers

by approx 6000 kilometers

15%

Created by: SpikeMe.
Statistics based on 26481 answers in 2 languages
»

## What is the volume of a soap bubble with radius R=1 cm?

4/3π cm3. Equation for the volume of a sphere: 4/3πR^3.

hard

58%

3/4π cm3

3/4π cm3

19%

4/3π cm3

4/3π cm3

58%

4,3π cm3

4,3π cm3

9%

It isn't possible to calculate

It isn't possible to calculate

12%

Created by: Paweł Kołodziejczyk.
Statistics based on 13796 answers in 2 languages
»

## Which shape is larger?

None of them. Both shapes are the same, but the bottom one is placed more to the right. This is however difficult to notice. It is known as Jastrow Illusion.

average

66%

A

A

2%

B

B

17%

None of them

None of them

66%

Both are larger

Both are larger

12%

Created by: globalquiz.org.
Statistics based on 32434 answers in 4 languages
»

## Which direction is not possible to point at when standing at the South Pole?

Neither east, west, nor south. At the South Pole every direction is north.

average

66%

east

east

2%

west

west

2%

north

north

27%

neither east, west, nor south

neither east, west, nor south

66%

Created by: globalquiz.org.
Statistics based on 17194 answers in 2 languages
»

## Which lines are parallel?

Green, blue and red. This is a well known Zöllner illusion, first described in 1860. It may be caused by this impression of depth. The black lines are parallel, too!

average

69%

blue and red only

blue and red only

4%

green and red only

green and red only

8%

green, blue and red

green, blue and red

69%

none

none

16%

Created by: globalquiz.org.
Statistics based on 20128 answers in 2 languages
»

## How many edges does a Möbius strip have?

One. The Möbius strip is a surface with only one side and only one boundary component (edge). A line drawn starting from the seam down the middle will meet back at the seam but at the "other side". If continued the line will meet the starting point and will be double the length of the original strip.

easy

72%

one

one

72%

two

two

18%

three

three

4%

four

four

3%

Created by: globalquiz.org.
Statistics based on 15978 answers in 4 languages
»

## How is this polygon called? (the one over the circles)

Square. In this Ehrenstein illusion the sides of a square placed inside a pattern of concentric circles take an apparent curved shape. But in reality, the sides are straight.

easy

74%

square

square

74%

rhomboid

rhomboid

10%

concave square

concave square

8%

concave rhomboid

concave rhomboid

6%

Created by: Debbie Fox.
Statistics based on 35465 answers in 2 languages
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## How many degrees an obtuse angle can have ?

90-180. The obtuse angle may measure from 90 to 180 degrees. Angles having a degree of 0 to 90 are acute angles, whereas those from 180 to 360 - concave angles.

easy

77%

0-360

0-360

3%

90-180

90-180

77%

0-90

0-90

2%

180-360

180-360

16%

Created by: TotalBellend.
Statistics based on 11428 answers in 2 languages
»

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