What is happening
You arrive at a chemist weighing out a prescription on a digital balance.
The pan reads 1.35 g and the prescription calls for exactly 2 g. Adding by eye keeps overshooting the second decimal place.
Decimal additionRunning
Mass on the pan
1.45g
Prescribed mass
2g
Mass on the pan is short by 0.55 g
Number line. Powder added at 0.1 g. Mass on the pan 1.45 g, Prescribed mass 2 g. Currently mass on the pan is short by 0.55 g.
What has to balance