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Clock Geometry

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Clock

Geometry

Half Past

Quarter Past

Quarter Till

How many hours does one revolution of the minute hand around the face of a clock represent?

How many hours does one revolution of the minute hand around the face of a clock represent?

1

How many minutes does one revolution of the minute hand around the face of a clock represent?

How many minutes does one revolution of the minute hand around the face of a clock represent?

60

If there are 12 numbers on a clock, how many minutes are there between 2 consecutive numbers?

If there are 12 numbers on a clock, how many minutes are there between 2 consecutive numbers?

60 ÷12=5

How many minutes are there between the numbers 12 and 6?

How many minutes are there between the numbers 12 and 6?

5x6=30

30 is what part of 60?

30 is what part of 60?

One half

How is another way to express the time 12:30?

How is another way to express the time 12:30?

Half past twelve

How many minutes are there between the numbers 12 and 3?

How many minutes are there between the numbers 12 and 3?

5x3=15

15 is what part of 60?

15 is what part of 60?

One quarter

How is another way to express the time 12:15?

How is another way to express the time 12:15?

Quarter past twelve

How many minutes are there between the numbers 9 and 12?

How many minutes are there between the numbers 9 and 12?

5x3=15

15 is what part of 60?

15 is what part of 60?

One quarter

How is another way to express the time 12:45?

How is another way to express the time 12:45?

Quarter till one

The Clock as

A Geometric

Figure

What geometric figure does the face of this clock represent?

What geometric figure does the face of this clock represent?

A circle

How many degrees are there in a circle?

How many degrees are there in a circle?

360°

How many minutes are there in one revolution of the minute hand?

How many minutes are there in one revolution of the minute hand?

60

If a clock can be seen as a circle, how many degrees does each minute represent?

If a clock can be seen as a circle, how many degrees does each minute represent?

360°÷60=6°

How many minutes are there between the numbers 12 and 1 on a clock?

How many minutes are there between the numbers 12 and 1 on a clock?

5

How many degrees are there between the numbers 12 and 1 on a clock?

How many degrees are there between the numbers 12 and 1 on a clock?

6°x5=30°

How many minutes are there between the numbers 12 and 3 on a clock?

How many minutes are there between the numbers 12 and 3 on a clock?

15

How many degrees are there between the numbers 12 and 3 on a clock?

How many degrees are there between the numbers 12 and 3 on a clock?

6°x15=90°

If we draw a line from the center of the clock to the number 12, another line from the number 12 to the number 3, and a third line from the number 3 back to the center of the clock, what geometric figure do we have?

If we draw a line from the center of the clock to the number 12, another line from the number 12 to the number 3, and a third line from the number 3 back to the center of the clock, what geometric figure do we have?

A triangle

If there are 90° between the number 12 and the number 3, how many degrees are there in the angle at the center of the circle?

If there are 90° between the number 12 and the number 3, how many degrees are there in the angle at the center of the circle?

90°

Can this triangle be called a right triangle?

Can this triangle be called a right triangle?

Yes, a right triangle is a triangle with one 90° angle.

If the three angles of a triangle add up to 180°, and the angle at the center of the circle is 90°, and the other two angles are equal, how many degrees are in each?

If the three angles of a triangle add up to 180°, and the angle at the center of the circle is 90°, and the other two angles are equal, how many degrees are in each?

180°-90°= 90°

90°÷2=45°

Is the distance between the center of a circle and any point on its circumference equal?

Is the distance between the center of a circle and any point on its circumference equal?

yes

Can this triangle be called an isosceles triangle?

Can this triangle be called an isosceles triangle?

Yes, an isosceles triangle is a triangle with two equal sides and two equal angles.

How many degrees are there between the numbers 5 and 7 on a clock?

How many degrees are there between the numbers 5 and 7 on a clock?

6°x10=60°

If we draw a line from the center of the clock to the number 5, another line from the number 5 to the number 7, and a third line from the number 7 back to the center of the clock, what geometric figure do we have?

If we draw a line from the center of the clock to the number 5, another line from the number 5 to the number 7, and a third line from the number 7 back to the center of the clock, what geometric figure do we have?

A triangle

If there are 60° between the number 5 and the number 7, how many degrees are there in the angle at the center of the circle?

If there are 60° between the number 5 and the number 7, how many degrees are there in the angle at the center of the circle?

60°

If the three angles of a triangle add up to 180°, and the angle at the center of the circle is 60°, and the other two angles are equal, how many degrees are in each?

If the three angles of a triangle add up to 180°, and the angle at the center of the circle is 60°, and the other two angles are equal, how many degrees are in each?

180°-60°= 120°

120°÷2=60°

Can this triangle be called an equilateral triangle?

Can this triangle be called an equilateral triangle?

Yes, a triangle with three 60° angles is an equilateral triangle.

Review

An hour has 60 minutes.

15 minutes make a quarter hour.

For 15 minutes after an hour we can say quarter past the hour.

4. For 45 minutes after an hour we can say quarter till the next hour.

5. For 30 minutes after an hour we can say half past the hour.

6. A circle has 360°.

7. Each minute on a clock represents 6° on the circumference of a circle.

8. A triangle has three sides.

9. A right triangle has one 90° angle.

10. An isosceles triangle has two equal sides and two equal angles.

11. An equilateral triangle has three equal sides and three 60° angles.

12. Geometry is everywhere. Just look for it!

Prepared by

Robert Janak

Beaumont,

Texas