Mathematical formula to obtain one's digit of an integer?

Question

I'm trying to create a mathematical formula to extract the rightmost (one's) digit of an integer.

So that f(245) =5, f(0) = 0, f(9999999)=9

Note, I'm looking for a formula, not an algorithm.

I tried messing around with base changes, and logarithms, but I'm probably just missing something obvious.

Answer 1

assuming you already have a formula for INT (integer - i.e. everything up to the decimal point) it would be :
x-10(INT(x/10))

Answer 2

6) That would be the 4, 13, 15 triangle with area 24. Second place tie 3, 25, 26 and 9, 10, 17 both with area 36.

Answer 3

Are you allowed to use the floor function?

Floor (99.8) = 99
floor (1.4) = 1
Floor (2.8) = 2

The formula to obtain the one's digit of an integer is

f(n) = n - 10*floor(n/10)

Answer 4

f(n) = n - 10 x int(n/10) with
n is an integer and
int(n/10) takes the whole ( = integer) part of n/10, so the fraction part has been left.

Th

Answer 5

if (5) =245, f(0) 99999= 45

Answer 6

f(x)=x mod 10

for x positive and

f(x)=10-(x mod 10)

for x negative.

Finding a formula that isn't an algorithm will be quite tricky because a formula is an algorithm.