# 10 most difficult mathematics riddles

A list of ten (out of 23) mathematics related questions that are the most often answered incorrectlyMathematics 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

24%

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

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

24%

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

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

19%

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

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

28%

Such solution doesn't exist

Such solution doesn't exist

27%

Created by: Paweł Kołodziejczyk.
Statistics based on 1745 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 3204 answers in 4 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

38%

19

19

38%

20

20

36%

21

21

19%

80

80

5%

Created by: Gizem İsmailoğlu.
Statistics based on 11173 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 9091 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

43%

by approx 6 meters

by approx 6 meters

43%

by approx 6 kilometers

by approx 6 kilometers

17%

by approx 60 kilometers

by approx 60 kilometers

21%

by approx 6000 kilometers

by approx 6000 kilometers

17%

Created by: SpikeMe.
Statistics based on 12538 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

47%

Albert Einstein

Albert Einstein

47%

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 7791 answers in 4 languages
»

## Which of the following numbers is the greatest?

1/3. Quite surprisingly, most players answer that both answers 1/3 and 33% are correct. But 1/3 is more than 33%. (it is 33.3333333...)

hard

52%

1/3

1/3

52%

0,3

0,3

4%

33%

33%

9%

Both answers 1/3 and 33% are correct

Both answers 1/3 and 33% are correct

33%

Created by: globalquiz.org.
Statistics based on 9132 answers in 2 languages
»

## What is the next number in the sequence? 2,3,5,7,11,13...

17. The sequence 2,3,5,7,11,13 includes prime numbers only. Many people incorrectly select 15, fooled by the fact that all prime numbers except 2 are odd.

hard

54%

15

15

35%

17

17

54%

19

19

5%

21

21

3%

Created by: Kasia.
Statistics based on 9843 answers in 2 languages
»

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