What is the measure, in degrees, of the smaller angle formed by the hour hand and the minute hand of a clock at 12:20?
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the irony is... some math teachers will answer 120 instead of 110...
they geometry rate is -1
Thanks Tom Li for giving such a clear explanation
No problem :D
Your solution is good but try mine, its simpler than yours (think so )
This was a common type of question that we used to ask our Year 7s. It's a good question that leads to harder questions.
Angle covered by MINUTE hand in 20 Minutes = 6 0 3 6 0 × 2 0 = 1 2 0 ∘
Angle covered by HOUR hand in 1hour = 1 2 3 6 0 × 1 = 3 0 ∘
Angle covered by HOUR hand in 20 Minutes = 6 0 3 0 × 2 0 = 1 0 ∘
Therefore, smaller angle formed by the hour hand and the minute hand of a clock at 12:20 = 1 2 0 ∘ - 1 0 ∘ = 1 1 0 ∘
heyhhey! Read your second line. (360/60)*1=30??? It should be 12 instead of 60 which means 360 degrees in 12 hours.
Sorry, it should be (360/12)*1 = 30 .
thanks for the best explanation
Your solution is good but try mine, its simpler than yours (think so )
I actually did it somewhat differently.....
If the hour hand did not move and stayed at the "12" position even at 12:20, the minute hand would (still) be at the "4" position and thus the angle would be 4 spaces, or 4/12, or 120 degrees.
However, since the hour hand does move, we know that the angle must be less than 120; thus, we can rule out the choices "120" and "130".
Since the hour hand moves 1/12 of the clock per hour, and 20 minutes (the 20 part of 12:20) is 20/60 of an hour, or 1/3, we do 3 1 × 1 2 1 = 3 6 1 = 3 6 0 1 0 = 1 0 degrees.
Since the answer must be less than 120, it must be 1 2 0 − 1 0 = 1 1 0
First calculate the angle between the minute hand and 12 'o' clock which comes to 120 degrees. Then, the angle made by the hour hand with 12 'o'clock comes to = (20/60x12) x 360 = 10 degrees. So the angle will be = 120-10 = 110 degrees
Para encontrar o ângulo entre os ponteiros do relógio podemos usar a seguinte fórmula: | 11m - 60h | /2 , onde m são os minutos e h são as horas. Substituindo os valores na fórmula temos: | 11.20 - 60.12| /2 = 250. Como queremos saber o menor ângulo bastar subtrair 250 de 360, que é igual a 110
Just by analyzing the clock, from 12 to 4 the angle between the hour hand and minute is equal to 120 degrees ( since the circle is divided equally into 12 spaces and the angle between spaces is 30 degrees.) At 12:20 the hour hand theoritically will travel (20/60)x30 = 10 degrees.. therefore from the figure the angle required is 120 - 10 = 110 degrees..
The formula for angle between two hands of a clock = ø = 30h – 11/2 m when minute hand is behind the hour hand or ø = 11/2 m – 30 h when it is ahead of hour hand. where h is hours completed and m is minutes completed.
at 12 O'clock h = 0 and m = 20 so a 12:20 ø = 11/2 m – 30h = 11/2 × 20 – 0 = 110°
for (12+20/60)hr angle traced by hour hand is (360/12)*(12+20/60)=370 degrees
Angle traced by mint hand in 20 min is (360/60)*20=120 degrees.
==>angle difference between them is 370-120=250 degrees.
but the min angle between them is 360-250=110 degrees
The hour hand goes exactly 1/12 times slower than the minute hand (that's why hour hand moves just a round while minute hand completes 12 round). a full round= 360 degree i.e. a minute step= 360/60=6 deg
the minute hand is at 20 min.
from 12 o clock it has moved 6*20=120 deg.
Meanwhile, the hour hand has moved from 12 o clock 120/12=10 deg.
i.e. the angle between them= 120-10 deg=110 deg
for every 10min there wil be a increase in 5 degree in hour hand. similarly wen 12.20. 12- 20 wil be 120 degree but the hour hand moves 10 degree so the value wil be 110 degree....
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The clock is 360 degrees (it's a circle), 360 / 12 (hours) = 30 degrees for each hour.
The short hand clock does not stop at 12 when its 12:20. 12:(20) is 1/3 of a clock which is 1/3 of a circle or 1/3 of 360 degree.
Thus 12:20 short hour hand is at 1/3 way to 1:00 .
12 to 12:20 is 30 degrees x 4 = 120 - (1/3 x 30) = 120 - 10 = 110
The clock is at 110 degrees when it's 12:20