Question

The length of a pencil is 15.1+/-0.1cm. A small part of it is cut and the length of the remaining pencil is 11.9+/-0.2cm. What is the length of the cut out part? The answer printed is 3.2+/- 0.1cm but i am getting 3.2+/- 0.3cm. This question is related to error analysis. Please help.

Answer 1

15.2-12.1=3.1 max possible values of both(15.1+0.1 and 11.9+0.2)
15.0-11.7=3.3 min possible value of both(15.1-0.1 and 11.9-0.2)
so 3.1 to 3.3 gives us 3.2+/-0.1

Answer 2

But the Rule of Subtraction says delta Z= delta X+delta Y

Answer 3

please provide a better explanation for my question....

Answer 4

i have explained dont just memorize formulas
here \[\Delta z= \Delta x + \Delta y \]
but here you have to subtract both terms
so
\[\Delta z = \Delta x - \Delta y \]