Explanation

The probability that someone is between Aviva and Naomi

• Aviva is the 37th person.

• Naomi is the 67th person.

• "Between" refers to people aged 37 to 67, i.e., positions 38 through 66.

Number of people between them = 66 − 38 + 1 = 29 people

There are 100 people total.

So the probability that a randomly chosen person is between them is:

$$\frac{\mathrm{<font\; color="\#0000ff"><span\; style="background-color:\; rgb(255,\; 255,\; 0);">29</span></font>}}{\mathrm{<span\; style="font-size:\; 0.875rem;"><font\; color="\#0000ff"\; style="background-color:\; rgb(255,\; 255,\; 0);">100</font><span\; style="font-family:\; Overpass,\; sans-serif;"></span></span>}}$$