Question

Which is the most reasonable estimate for the length of an index (pointer) finger?

eight decimeters

eight centimeters

eight millimeters

eight kilometers

Answer 1

This is a funny question when you are used to the metric system. Think that a meter is very roughly your arm streched out. Then deci- means tenth, centi- means a hundredth, milli- means a thousandth and kilo means thousand.

Answer 2

Do the process of elimination.

You know that millimetres, are very small and our index fingers aren't that small.
Decimetres are higher in length and even higher than centimetres.
Kilometres are practically measured for traveling in a very long distance.

So I would say that the most reasonable estimate would be eight centimetres.