Taking Precise Measurements

1. Each measuring device has limits to its own precision.
2. You can only estimate one digit between known markings.
   
   
   Because we know the arrow is between 0.1m and 0.2m we can estimate the next digit.
   
   
3. On a more finely marked ruler we can get more precise measurements.
   
   Now we know the mark is between 0.12m and 0.13m, so we can estimate one more digit.
   
   
4. If the arrow falls directly on one of the ruler lines then the measurement of that arrow should have the same precision as any other measurement on the ruler. You may have to add zeros to make this true.
   
   Notice that the measurement is 0.30m, not 0.3m.
   
   
   Again, notice that the number of digits (or precision) in the two measurements is the same.