Use division instead of multiplication Is there any way to calculate x/y without using division? Like 1/10 = 1 * 0.1  . I'm asking because dividing is slower than multiplying in programming programs.
 A: No. There's no free lunch: the most efficient way to calculate $x/y$ for general $y$ is to ask the hardware to divide $x$ by $y$.
Obviously, in analogy to your example, $x/y = x \cdot \frac{1}{y}$ if you happen to have $\frac{1}{y}$ handy. Maybe if you're dividing many, many numbers by the same $y$, inverting $y$ first and then doing a bunch of multiplications will save some cycles. But see my caveat below.
Another special case is when $y$ is an integer power of 2: division can then be efficiently performed using bit shifting, if $x$ is also an integer, or by adjusting the exponent of $x$, if $x$ is an IEEE floating point number of the form $a 2^{b}$.
CAVEAT: Please do not try to "optimize division" by hand:


*

*The compiler you are using is very good at recognizing special cases where division can be optimized / replaced by faster operations and will almost certainly do a better job at it than you. 

*Division is extremely unlikely to be the biggest performance bottleneck in your program, so spending time optimizing it isn't spending your time most effectively.

*Your future self, and anyone else who needs to maintain your code in the future, will thank you for writing more straightforward, readable code.
A: I'm sure this is not the answer you're looking for, but (for $x, y, b > 0$) there's always
$$ x/y = b^{\log_b(x) - \log_b(y)}$$
which (with $b=10$ and using log tables) was the usual way division with about  5 digit precision was performed in the days before computers.
A: (Can't comment) That number will lead you down the path of wisdom 7EF127EA. Perhaps we should ask ourselvs. Is rediscovering the wheel another form of procrastion for the intellectually inclined? Also be sure to check also this.
