# 10 most difficult mathematics riddles

A list of ten (out of 25) mathematics related questions that are the most often answered incorrectly

Mathematics quiz
## Which of the following is true for the solution with the pH=0?

The OH − ion concentration is smaller than the H+ ion concentration. In chemistry, pH is a numeric scale used to specify the acidity or alkalinity of an aqueous solution. It is the negative of the logarithm to base 10 of the activity of the hydrogen ion .Traditionally the pH is being defined as: pH = - log10 [H+], where [H+] it is a H+ ions concentration in mol/dm^3 (M). So if pH = 0 this H+ ions concentration is 1 mol/dm^3 and the solution is strongly acidic.

very hard

25%

the OH − ion concentration is smaller than the H+ ion concentration

the OH − ion concentration is smaller than the H+ ion concentration

25%

the OH − ion concentration is greater than the H+ ion concentration

the OH − ion concentration is greater than the H+ ion concentration

20%

the OH − ion concentration is equal of the H+ ion concentration

the OH − ion concentration is equal of the H+ ion concentration

27%

Such solution doesn't exist

Such solution doesn't exist

26%

Created by: Paweł Kołodziejczyk.
Statistics based on 2176 answers in 2 languages
»

## Who introduced the Fibonacci numbers?

Leonardo of Pisa, also known as Leonardo Fibonacci, Leonardo Pisano Bigollo. His 1202 book Liber Abaci introduced the sequence to Western European mathematics,[6] although the sequence had been described earlier as Virahanka numbers in Indian mathematics.

very hard

25%

Edouard Lucas

Edouard Lucas

9%

Cartesius

Cartesius

28%

Gottfried Wilhelm Leibniz

Gottfried Wilhelm Leibniz

36%

Leonardo of Pisa

Leonardo of Pisa

25%

Created by: Ola.
Statistics based on 429 answers in 2 languages
»

## Which of the following Roman numerals stands for 4?

Both IV and IIII. Both notations are correct and historically Roman numerals were often written less consistently than today. The notation 'IIII' is often seen on clock faces. The reason for that may be practical, to avoid confusing the IV and VI when the clock is held upside down (although other theories also exist).

very hard

28%

IV

IV

68%

IIII

IIII

1%

Both IV and IIII

Both IV and IIII

28%

None of the above

None of the above

1%

Created by: globalquiz.org.
Statistics based on 3701 answers in 4 languages
»

## Which numeral system was in use in ancient Sumer and Babilon?

Sexagesimal. Remnants of highly composite sexagesimal system are in use even today for measuring angles, geographic coordinates and especially time. An hour of time is divided into 60 minutes, which in turn are divided into 60 seconds.

very hard

32%

octal

octal

21%

binary

binary

19%

decimal

decimal

25%

sexagesimal

sexagesimal

32%

Created by: smyru.
Statistics based on 9362 answers in 2 languages
»

## Augustus was born on 1 January 10BC. Which birthday did he celebrate at 1 January 10AD?

19. There was no year number zero. There were only 1999 years between 1000BC and 1000AD.

very hard

39%

19

19

39%

20

20

35%

21

21

19%

80

80

5%

Created by: Gizem İsmailoğlu.
Statistics based on 12649 answers in 4 languages
»

## Typically, how many leap years are in a century?

24. The Gregorian Calendar omits 3 leap days every 400 years, omitting February 29 in the 3 century years (integer multiples of 100) that are not also integer multiples of 400. For example, 1600 was a leap year, but 1700, 1800 and 1900 were not. Similarly, 2000 was a leap year, but 2100, 2200, and 2300 will not be.

hard

43%

20

20

9%

24

24

43%

25

25

42%

100

100

4%

Created by: ex-terminator.
Statistics based on 10537 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

16%

by approx 60 kilometers

by approx 60 kilometers

20%

by approx 6000 kilometers

by approx 6000 kilometers

16%

Created by: SpikeMe.
Statistics based on 15935 answers in 2 languages
»

## Which famous scientist was born on the Pi day? (March 14)

Albert Einstein. 14 of March is celebrated on many schools and universities as both Pi Day and the birthday of Albert Einstein. On of the traditions is the 'Pi Pie' (pictured).

hard

48%

Albert Einstein

Albert Einstein

48%

Blaise Pascal

Blaise Pascal

17%

Isaac Newton

Isaac Newton

17%

all of the above

all of the above

17%

Created by: globalquiz.org.
Statistics based on 9155 answers in 4 languages
»

## How many possible code combinations are there for this kind of lock?

10000. The possible codes are from 0000 to 9999 inclusive. There are 10 possibilities for each ring, thus there are 10*10*10*10 possible codes.

hard

51%

999

999

5%

1000

1000

6%

9999

9999

36%

10000

10000

51%

Created by: Teddy.
Statistics based on 9690 answers in 2 languages
»

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