1. Precision in Measurement
When we measure, we always add one digit BEYOND the last known measurable digit
-- That digit is called the first uncertain digit
FOR EXAMPLE:
On the ruler above, the arrow is pointing between 2.4 and 2.5 cm cm is the last known digit. We also must add the first uncertain digit to show that our measurement is greater than 2.4, but less than 2.5 cm.
Therefore, the most correct measurement would be something like 2.46 cm

2. Precision in Measurement
When we measure, we always add one digit BEYOND the last known measurable digit
-- That digit is called the first uncertain digit
FOR EXAMPLE:
On the ruler above, the arrow is pointing between 2.4 and 2.5 cm cm is the last known digit. We also must add the first uncertain digit to show that our measurement is greater than 2.4, but less than 2.5 cm.
Therefore, the most correct measurement would be something like 2.46 cm