Question

When you describe a quantity with more than one familiar unit (such as kilometers or millimeters for a length), how can you decide which is a more appropriate unit to use? While it is not incorrect to use the less appropriate unit, why do you want to avoid using it anyway?

Answer 1

You can decide by seeing which one measures object better. you want to avoid using the incorrect unit because it can meaure it wrong or it won't be as accurate as the right unit

Answer 2

When we use smaller units to describe something bigger, it becomes lengthy and confusing to calculate.

Like, if we want to tell the weight of a truck, it is better to use tons rather than grams.

Because 1 ton has 907185 grams approx. So, you can see the calculation becomes long, if we want to convert 5 tons to grams and it will be difficult to say that a truck weighs 4.536e+6 grams.

This is why we avoid using smaller units for larger things.