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Tuesday, July 26, 2011
Monday, July 25, 2011
Formula Answers
1. What is the equation of a line? y = mx + b m = slope and b = y-intercept
2. The slope formula? m = change in y / change in x or (y2 - y1)/(x2-x1)
3. Circumference of a circle? C = 2 pi r
4. Area of a circle? A = pi r squared
Thursday, July 21, 2011
July 2011 Brain Teaser Solution
How many degrees are in the acute angle formed by the hands of a clock at 2:20PM?
A: 50 degrees
A circle has 360 degrees, so each of the 12 hours on the clock is 30 degrees (360/12)
Exactly 2:00 is 60 degrees from the twelve while 4:00 is 120 degrees. So the difference between 2 and 4 would be 60 degrees EXCEPT that as the minute hand goes around the clock, the hour hand moves between the hours.
So while the long hand is exactly pointing at the 4, the little hand is in between the 2 and 3. As it is 20 minutes past the hour, 1/3 of the hour has elapsed.
Since there is 30 degrees in between the 2 and the 3 and it has only transversed 1/3 of 30, it is 10 degrees closer than it was at exactly 2.
BTW, an acute angle is less than 90 so 50 fits the bill. The angle going counterclockwise is 360 - 50 = 310.
A: 50 degrees
A circle has 360 degrees, so each of the 12 hours on the clock is 30 degrees (360/12)
Exactly 2:00 is 60 degrees from the twelve while 4:00 is 120 degrees. So the difference between 2 and 4 would be 60 degrees EXCEPT that as the minute hand goes around the clock, the hour hand moves between the hours.
So while the long hand is exactly pointing at the 4, the little hand is in between the 2 and 3. As it is 20 minutes past the hour, 1/3 of the hour has elapsed.
Since there is 30 degrees in between the 2 and the 3 and it has only transversed 1/3 of 30, it is 10 degrees closer than it was at exactly 2.
BTW, an acute angle is less than 90 so 50 fits the bill. The angle going counterclockwise is 360 - 50 = 310.
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