Answer:
(D) 4×10⁻³
Explanation:
The difference is ...
0.2050 -0.2014 = 0.0036 = 3.6×10⁻³
The number 0.205 is expressed to a precision of 1×10⁻³, so the result of the subtraction operation cannot be considered to be more precise. It must be expressed as ...
4×10⁻³ . . . . matches choice D
_____
Additional comment
This is physics, not math. In the physical sciences, most numbers must be considered to be measurements. (A few are definitions.) Hence, the rules of significant figures and precision apply to the results of arithmetic operations. This problem is a good illustration of what happens when computing small differences of large numbers. We start with 3 significant figures in 0.205, and end up with 1 significant figure in 0.004.
