Question

You are attempting to estimate the number of protester marching through the city

street. You station yourself at the beginning of the protest march. You count 177
protesters within the first 2.1 minutes. Finally, after 12 minutes all of the protesters have
passed you by. What would be a good estimate for the number of protesters given this
information?

Answer 1

9514 1404 393

Answer:

1000

Explanation:

If the number of protesters per minute remains a constant, then you could write the proportion ...

p/12 = 177/2.1

Multiplying by 12 gives ...

p = 12(177/2.1) ≈ 1011.4

Here, minutes are given to 2 significant figures, and the initial count is given to 3 significant figures. The best you can hope for is that your estimate is good to 3 significant figures:

1010 protesters

It is probably sufficient to report the number to 2 significant figures*:

1000 protesters

_____

* Unfortunately, with a number like 1000, the only way you can tell it has 2 significant figures is to report it as 1.0×10³ or 10. hundreds. The trailing zeros are usually not considered significant.