# Computing Percentages Easier

DevFeed: [Computing Percentages Easier](<https://devfeed.tech/articles/computing-percentages-easier-40472.md>)

Original publisher: [Read original article](<https://www.jeremykun.com/2023/09/05/computing-percentages-easier/>)

Published: 2023-09-05T21:47:37Z

Content type: tutorial

Language: en

Sources: [Jeremy Kun](<https://devfeed.tech/sources/jeremy-kun.md>)

Topics: [math](<https://devfeed.tech/topics/math.md>), [Computing](<https://devfeed.tech/topics/computing.md>)

Tags: [approach](<https://devfeed.tech/tags/approach.md>), [arithmetic](<https://devfeed.tech/tags/arithmetic.md>), [math](<https://devfeed.tech/tags/math.md>), [mathematics](<https://devfeed.tech/tags/mathematics.md>), [numbers](<https://devfeed.tech/tags/numbers.md>), [puzzle](<https://devfeed.tech/tags/puzzle.md>), [scaling](<https://devfeed.tech/tags/scaling.md>)

## AI overview

A math tutorial explains mental percentage calculations using the fact that x% of y equals y% of x. It presents several approaches, including choosing the easier percentage, multiplying first and dividing by 100, scaling from 1%, and splitting the denominator.

## Source excerpt

Problem: Compute 16% of 25 in your head. Solution: 16% of 25 is equivalent to 25% of 16, which is clearly 4. This is true for all numbers: $x\%$ of $y$ is always equal to $y\%$ of $x$. The first one is $\frac{x}{100} y$ and the second is $\frac{y}{100}x$, and because multiplication is commutative and associative, both are equal to $(x \cdot y) / 100$. You can pick the version that is easiest.