# Why do we use division when we use per something?

1. Oct 10, 2015

### Cash Fulton

Why do we use division/fractions to represent per something?

2. Oct 10, 2015

### phinds

Three per hundred, for example, means 3 out of 100, so we can write it as a ratio, 3:100, or a fraction, 3/100

3. Oct 10, 2015

### pasmith

3 per hundred is 3:97.

4. Oct 10, 2015

### phinds

Ah yes, good catch. I should have said "three out of a hundred, or 3/100"

5. Oct 10, 2015

### Cash Fulton

Doesn't really answer my question. I am asking why that is.

6. Oct 10, 2015

### Staff: Mentor

Why it is, is because of what the words mean. When we say, for example, 6 per cent (literally 6 per 100) we are expressing a ratio: $\frac 6 {100}$. It's similar for units such as mph (miles per hour). We are talking about a ratio of miles driven per (divided by) the time in hours.

7. Oct 10, 2015

### symbolipoint

"per" distinctly indicates both DIVISION and FRACTION.