Why were standard units introduced?

Which statement correctly describes a non-physical quantity?

Which of the following is a complete measurement?

Which rounding rule applies when the first dropped digit is less than 5?

Which SI base unit and symbol are correctly matched?

When rounding off, if the first dropped digit is greater than 5, the retained digit is:

Which derived unit is equivalent to metre per second?

If repeated readings are close to each other but not near the true value, they are:

Which prefix represents 10^-9?

Accuracy of a measurement means:

A time interval of 2000 microseconds is equal to: