Answer:
[tex]\frac{5\pi}{3}\:\mathrm{radians}[/tex]
Step-by-step explanation:
Each complete revolution of a circle is equal to [tex]2\pi[/tex] radians. The minute-hand travels one of these revolutions in 60 minutes. Since there are 50 minutes from 12:40 PM to 1:30 PM, the minute hand travels [tex]\frac{50}{60}\cdot 2\pi=\frac{100}{60}\cdot 2\pi=\boxed{5\pi/3\:\mathrm{radians}}[/tex]
