Modulo Operation/Examples/100 mod 7

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Theorem

$100 \bmod 7 = 2$

where $\bmod$ denotes the modulo operation.


Proof

By definition of modulo operation:

$x \bmod y := x - y \left \lfloor {\dfrac x y}\right \rfloor$

for $y \ne 0$.


We have:

$\dfrac {100} 7 = 14 + \dfrac 2 7$

and so:

$\left\lfloor{\dfrac {100} 7}\right\rfloor = 14$


Thus:

\(\displaystyle 100 \bmod 7\) \(=\) \(\displaystyle 100 - 7 \times \left\lfloor{\dfrac {100} 7}\right\rfloor\)
\(\displaystyle \) \(=\) \(\displaystyle 100 - 7 \times 14\)
\(\displaystyle \) \(=\) \(\displaystyle 2\)

$\blacksquare$


Sources