Question

A baker bakes a cake and expects it to weigh 2.5 kg. After baking, he weighs the cake and finds it weighs 2.25 kg. Later, he remembers that the scale he used reads 5% lower than the actual weight.

Question:

What is the observed percentage error based on the scale reading?

What is the true percentage error after correcting for the scale’s error?

Answer 1

Observed error (from scale reading) = (2.25 − 2.5)/2.5 × 100% = −0.25/2.5 ×100% = −10% (10% short).

Corrected (true) weight = 2.25/0.95 = 2.368421... kg.
True percentage error = (2.368421 − 2.5)/2.5 ×100% ≈ −5.263% (about 5.26% short).