A watch gains 5 minutes in every hour. How many degrees does its second hand move in one (true) minute?

Introduction / Context:
A correct second hand completes 360° per true minute. A fast watch completes more revolutions per true minute. With a gain of 5 minutes per hour, the faster dial covers 65 indicated minutes in 60 true minutes.

Given Data / Assumptions:

• Gain = 5 min per 60 min.
• Second hand turns 360° per indicated minute.

Concept / Approach:
Revolutions per true minute = 65/60. Degrees per true minute = (65/60) * 360.

Step-by-Step Solution:
Degrees/min = (65/60) * 360 = 65 * 6 = 390°.

Verification / Alternative check:
If it were correct, it would be 360°; since it is faster, 390° makes sense.

Why Other Options Are Wrong:
375°, 380°, 365° underestimate; 360° ignores the gain.

Common Pitfalls:
Adding 5° instead of proportionally scaling revolutions.

Final Answer:
390°