Addition & Subtraction of Errors

Q. How are random errors minimised?

Q.

The mass of Mr x is 50kg and the uncertainty in measurement is 1 kg.The mass of Mr y is 55kg and the uncertainty in measurement is 2 kg. Find the difference of their masses with correct uncertainties.

1. 105 $\pm$ 3 kg

2. 5 $\pm$ 1 kg

3. 5 $\pm$ 3 kg

4. None of these