The World’s fastest on a computer writes a bit more than 210 words per minute;^{[1]} more than 210 words during those 60 seconds that one minute lasts.

How many words is that every *second*? Let’s split the 210 words into 60 bits by using a slash $/$ as ‘split into’:

$$210\,\text{words}\,/\,60\,\mathrm s=3\,\text{words/s}$$

In other words, we have used the slash $/$ to mean ‘per’ or ‘divided by’.^{1} We can call this operation a **division**. ‘210 words **divided by** 60 seconds’ or ‘210 words **per **60 seconds’ is ‘3 words **per** second’. The slash even works in this new combined version of a unit: $\text{words/s}$, meaning ‘words per second’.^{2}

Note that division ( $/$ ) and multiplication ( $\cdot$ ) are each other’s “reverse”. ‘To divide’ splits into smaller portions, whereas ‘to multiply’ collects portions again. The 3 words per second will be 210 words after 60 seconds because 3 **times **60 is 210.

To give a better overview, especially when writing longer lines, we could choose to tilt the slash down to a horizontal line and write it like:

$$\frac{210\,\text{words}}{60\,\mathrm s}= 3\,\text{words/s} $$

This writing-style is well-known from for example when we write ‘a half’ as $\frac12$. Let’s call it a **fraction **and the horizontal line a **fraction bar**.^{3}

- Let’s call the bottom of a fraction the
**denominator**^{4}since it*names*the fraction (it tells us if we are splitting into thirds, fourths or fifths etc.; for instance, $\frac18$ is one**eighth**and $\frac38$ is three**eighths**), and - let’s call the top the
**numerator**,^{5}since it*counts*the fractions ($\frac18$ is**one**eighth and $\frac38$ is**three**eighths).

References:

- ‘
**Average typing speed infographic**’ (web page), Free Online Typing Tutor, www.ratatype.com/learn/average-typing-speed (accessed Aug. 5th, 2019) - ‘
**Online Etymology Dictionary**’ (dictionary),*Douglas Harper*, www.etymonline.com