New posts in arithmetic

Riddle (simple arithmetic problem/illusion)

Why does the symbol for the multiplication operation change shape?

Factorial, but with addition [duplicate]

Formal proof for $(-1) \times (-1) = 1$

Root Calculation by Hand

How to convince a math teacher of this simple and obvious fact?

$4494410$ and friends

Why is $\frac{987654321}{123456789} = 8.0000000729?!$

Why is there no "remainder" in multiplication

Why not to extend the set of natural numbers to make it closed under division by zero?

How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen?

Apparently sometimes $1/2 < 1/4$?

Why does an argument similiar to 0.999...=1 show 999...=-1?

Is there another simpler method to solve this elementary school math problem?

Proof that ${\left(\pi^\pi\right)}^{\pi^\pi}$ (and now $\pi^{\left(\pi^{\pi^\pi}\right)}$) is a noninteger.

Why is negative times negative = positive?

Division by zero

What is $48\div2(9+3)$? [duplicate]

Why does this innovative method of subtraction from a third grader always work?

Solving linear congruences by hand: modular fractions and inverses