Answer:
(3.5, 4.5)
Step-by-step explanation:
The masses have a total margin of 0.5 kg, or ±0.25 kg.
The mass of the first parcel is 1.5 kg ± 0.25 kg.
The mass of the second parcel is 2.5 kg ± 0.25 kg.
The combined mass is:
(1.5 kg + 2.5 kg) ± (0.25 kg + 0.25 kg)
4 kg ± 0.5 kg
So the lower bound is 3.5 kg and the upper bound is 4.5 kg.
