Difference between revisions of "1955 AHSME Problems/Problem 2"
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==Solution== | ==Solution== | ||
At <math>12:25</math>, the minute hand is at <math>\frac{25}{60}\cdot 360^\circ</math>, or <math>150^\circ</math>. | At <math>12:25</math>, the minute hand is at <math>\frac{25}{60}\cdot 360^\circ</math>, or <math>150^\circ</math>. | ||
− | The hour hand moves <math>5</math> 'minutes' every hour, or <math>\frac{5}{60}\cdot 360 = 30^\circ</math> every hour. At <math>30^\circ</math> every hour, the hour hand moves <math>\frac{1}{2}</math> minutes on the clock every minute. At <math>12:25</math>, the hour hand is at <math>\frac{25}{2}^\circ</math>. Therefore, the angle between the hands is <math>150^\circ - \frac{25}{2}^\circ</math>, <math>137.5^\circ</math>, or <math>137^{\circ} 30^{'} \implies \boxed{\mathrm{(B) 137^\circ 30'}}</math>. | + | The hour hand moves <math>5</math> 'minutes' every hour, or <math>\frac{5}{60}\cdot 360 = 30^\circ</math> every hour. At <math>30^\circ</math> every hour, the hour hand moves <math>\frac{1}{2}</math> minutes on the clock every minute. At <math>12:25</math>, the hour hand is at <math>\frac{25}{2}^\circ</math>. Therefore, the angle between the hands is <math>150^\circ - \frac{25}{2}^\circ</math>, <math>137.5^\circ</math>, or <math>137^{\circ} 30^{'} \implies</math> <math>\boxed{\mathrm{(B) 137^\circ 30'}}</math>. |
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+ | ==Solution 2== | ||
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+ | Using the formula <math>\frac{|(60h-11m)|}{2}</math>, and plugging in 12 for h and 25 for m, we get the angle between to be 222.5<math>^{\circ}</math>. Since the problem wants the smaller angle, we do <math>360-222.5 = 137.5 \Rightarrow 137^{\circ}30'\Rightarrow \fbox{B}</math> | ||
==See Also== | ==See Also== |
Latest revision as of 12:37, 4 May 2020
Contents
Problem
The smaller angle between the hands of a clock at p.m. is:
Solution
At , the minute hand is at , or . The hour hand moves 'minutes' every hour, or every hour. At every hour, the hour hand moves minutes on the clock every minute. At , the hour hand is at . Therefore, the angle between the hands is , , or .
Solution 2
Using the formula , and plugging in 12 for h and 25 for m, we get the angle between to be 222.5. Since the problem wants the smaller angle, we do
See Also
1955 AHSC (Problems • Answer Key • Resources) | ||
Preceded by Problem 1 |
Followed by Problem 3 | |
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All AHSME Problems and Solutions |
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