Maths Logic

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10




Similar Riddles

In the attached figure, you can see a chessboard and two rooks placed on the chess board. What you have to find is the number of squares that do not contain the rooks. How many are there?

Squares in Chess Board

Asked by Neha on 04 Mar 2024


Can you decipher the two rows to find the hidden word?


Make the Word

Asked by Neha on 14 May 2021

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

Asked by Neha on 23 Apr 2023


Rahul decided to meet Simran so he boards a local train from Bombay station. Just after the station, there is a 1km long tunnel. The train starts and is now accelerating. Rahul is a claustrophobic guy, so what is the best position for him to sit?

Asked by Neha on 25 Mar 2023

In which direction should the missing arrow point?

Arrow Direction

Asked by Neha on 30 Dec 2024

Can you identify the famous TV character from the rebus below?

Uncover TV character

Asked by Neha on 22 Nov 2023


Six people park their car in an underground parking of a store. The store has six floors in all. Each one of them goes to a different floor. Simon stays in the lift for the longest. Sia gets out before Peter but after Tracy. The first one to get out is Harold. Debra leaves after Tracy who gets out on the third floor.

Can you find out who leaves the lift on which floor?

Asked by Neha on 24 Dec 2024

John and Jenni are a married couple. They have two kids, one of them is a girl. Assume safely that the probability of each gender is 1/2.
What is the probability that the other kid is also a girl?

Hint: It is not 1/2 as you would first think.

Asked by Neha on 14 Jun 2024

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

Asked by Neha on 16 Mar 2024


A thief is convicted in Mexico. He gets the death penalty. The judge allows him to say the last sentence to determine how the penalty will be carried out. If the thief lies, he will be hanged, if he speaks the truth he will be beheaded. The thief tells the last sentence and to everybody's surprise some minutes later he is set free because the judge cannot determine his penalty. What did the thief say?

Asked by Neha on 07 Sep 2024

Hot Articles

Amazing Facts

Out of the Box

The phrase “thinking outside the box” was popularised from the solution to a topographical puzzle involving 9 dots in a box shape.