The term "triple" means to multiply a given number by 3. The "triple" of a number is the result multiplying the number by 3. For example, if we were to triple the number 2, we would get 6:
2 × 3 = 6
Tripling a number is also equivalent to adding that number to itself an additional two times.
2 + 2 + 2 = 2 × 3 = 6
Another way to think of this is having 3 groups of something.
In the figure below, we can look at multiplication by 3 as the addition of 3 groups consisting of 2 squares each. Tripling one group of two squares is the equivalent of adding another two equal groups to get 1 group of 6 squares.
In the context of geometry, a triple most often refers to a Pythagorean triple. A Pythagorean triple is a group of three integers that fulfills the Pythagorean theorem
a2 + b2 = c2
where a, b, and c are positive integers such that c is the largest of the three.
Confirm that 3, 4, 5 is a Pythagorean triple:
32 + 42 = 52
9 + 16 = 25
25 = 25
The above is a true statement, so 3, 4, 5 is a Pythagorean triple.