Explore the parity of sums, calculate digital roots, and solve Cryptarithm puzzles.
The Parity of 4 Consecutive Numbers
Choose a starting number, then click the signs to toggle them between addition and subtraction. Watch the result!
3
4
5
6
=
8
Result is Even.
When you switch a sign (e.g., from +4 to -4), you change the total sum by twice that number (e.g., -8). Since twice any number is an even number, changing signs only adds or subtracts even amounts. Therefore, the parity (even or oddness) of the sum never changes!
Digital Roots & Divisibility
The Digital Root is found by repeatedly summing the digits of a number until a single digit remains. Click a number in the grid to see the process!
Select a number below
Cryptarithms: Digits in Disguise
Each letter represents a unique digit (0-9). The first digit of a number cannot be 0. Drag digits from the pool into the slots to solve the puzzle!