What will be the absolute error of a measurement of at least 1 mm on a scale?

Correct answer: c 0.05 cm

When the finest division is 1 mm the absolute error is half of it = 0.5 mm = 0.05 cm.

Why the other options are wrong

• a 0.1 mm: 0.1 mm is one tenth of 1 mm; the absolute error is half of the finest division, 0.5 mm.
• b 1 mm: 1 mm is the whole division itself; the absolute error is half of it, 0.5 mm.
• d 0.5 cm: 0.5 cm = 5 mm, five times 1 mm; the error is 0.5 mm, not 0.5 cm.