Analog Clock Problem 2

Geometry Level 3

Nelson took a picture of his analog clock at exactly 12 12 : : 00 00 AM \text{AM} and took another picture after one second.

In the second picture, how far apart (in degrees (°)) are the hands from each other?

Note: Compute for the acute angle. The answer should be rounded to the nearest ten-thousandths.


The answer is 0.0917.

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2 solutions

Jordan Cahn
Feb 26, 2019
  • The minute hand moves 1 s × 1 min 60 s × 36 0 60 min = 0. 1 1\text{ s}\times \dfrac{1\text{ min}}{60 \text{ s}}\times\dfrac{360^\circ}{60\text{ min}} = 0.1^\circ
  • The hour hand moves 1 s × 1 min 60 s × 1 h 60 min × 36 0 12 h = 0.008 3 1\text{ s}\times \dfrac{1\text{ min}}{60 \text{ s}}\times \dfrac{1\text{ h}}{60 \text{ min}} \times\dfrac{360^\circ}{12\text{ h}} = 0.008\overline{3}^\circ

Thus, the angle between the two is 0. 1 0.008 3 0.091 7 0.1^\circ-0.008\overline{3}^\circ \approx \boxed{0.0917^\circ} .

Kaizen Cyrus
Feb 23, 2019

Through computation, the minute-hand moves 0.1 ° 0.1° every second while the hour-hand moves 0.008 3 ˉ ° 0.008\bar{3}° every second. At 12 12 : : 00 00 AM \text{AM} , if the 12 12 marking of the clock is 0 ° , the hour-hand would've moved 0.008 3 ˉ ° 0.008\bar{3}° and the minute-hand would've moved 0.1 ° 0.1° after a second. Their gap would be 0.1 ° 0.008 3 ˉ ° 0.0917 degrees 0.1°-0.008\bar{3}°\approx\boxed{0.0917}\space\text{degrees} .

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