10 most difficult numbers riddles A list of ten (out of 25) numbers related questions that are the most often answered incorrectly Numbers quiz 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 25% IVIV71%IIIIIIII1%Both IV and IIIIBoth IV and IIII25%None of the aboveNone of the above1%Created by: globalquiz.org. Statistics based on 6048 answers in 4 languages »ancient Rome riddles » 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 concentrationthe OH − ion concentration is smaller than the H+ ion concentration25%the OH − ion concentration is greater than the H+ ion concentrationthe OH − ion concentration is greater than the H+ ion concentration20%the OH − ion concentration is equal of the H+ ion concentrationthe OH − ion concentration is equal of the H+ ion concentration28%Such solution doesn't existSuch solution doesn't exist26%Created by: Paweł Kołodziejczyk. Statistics based on 3243 answers in 2 languages »mathematics riddles » 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% octaloctal22%binarybinary20%decimaldecimal24%sexagesimalsexagesimal32%Created by: smyru. Statistics based on 13154 answers in 2 languages »ancient history riddles » Which currency was the first to be converted to decimal system?Russian ruble. The new ruble introduced with monetary reform of Peter the Great of 1704 was the first currency to be based on decimal system.hard 40% American dolarAmerican dolar13%British pound sterlingBritish pound sterling21%frank of revolutionary Francefrank of revolutionary France23%Russian rubleRussian ruble40%Created by: smyru. Statistics based on 7297 answers in 2 languages »coins riddles » What's the distance between USA and Russia?4 Km / 2.5 miles . Alaska is only 2.5 miles away from Russiahard 40% 4 Km / 2.5 miles 4 Km / 2.5 miles 40%40 Km / 25 miles40 Km / 25 miles25%400 Km / 250 miles400 Km / 250 miles15%4000 Km / 2500 miles4000 Km / 2500 miles17%Created by: grifi bastion. Statistics based on 953 answers in 2 languages »USA riddles » What is approximate distance from Gdańsk (Poland) to Gogolewo (Russia) in a straight line?Ok. 100 km. Gogolewo is located in the Kaliningrad Oblast, so the distance is small.hard 40% ok. 10 kmok. 10 km10%ok. 100 kmok. 100 km40%ok. 1000 kmok. 1000 km23%ok. 10000 kmok. 10000 km25%Created by: lukasz Poland. Statistics based on 559 answers in 2 languages »Poland riddles » 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 42% 20209%242442%252544%1001004%Created by: ex-terminator. Statistics based on 15410 answers in 2 languages »calendar riddles » Result calculation 2*3! is equal to: 12. Sign ! it is factorial. Means that number (here: 3) is multiplication by all previous numbers (not 0) (here: 1*2*3) , so: 2*3!= 2*(1*2*3)= 2*6= 12 hard 45% 6635%121245%24246%None of the answers are correctNone of the answers are correct13%Created by: lukasz Poland. Statistics based on 2846 answers in 2 languages »author: lukasz Poland riddles » After adding to some number half her worth and next calculate her the root we will get it half. What's the number?6. 1.After adding to some number half her worth: 6 + 3 =9 2.Next calculate her the root we will get it half: √9 = 3 | 6 : 3 = 0,5 (half)hard 46% 1115%4432%6646%10105%Created by: lukasz Poland. Statistics based on 237 answers in 2 languages »elements riddles » Who created Fibonacci Sequence?All of the answers are correct. Leonardo of Pisa was also known as:Leonardo Fibonacci, Filiu Bonacci, Leonardo Pisano. He was son of Guillaume Bonacci. He lived ok.1175 - 1250. He was Italian matematician.hard 47% son of Guillaume Bonacci son of Guillaume Bonacci 10%Filius BonacciFilius Bonacci21%Leonardo of PisaLeonardo of Pisa21%All of the answers are correctAll of the answers are correct47%Created by: lukasz Poland. Statistics based on 360 answers in 2 languages »curiosities riddles » Play numbers quiz and see all the questions.