Circles And Anglesmath Problem Solving



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Circles And Anglesmath Problem Solving

Draw a circle with a diameter (all the way across the circle) of 1

Then the circumference (all the way around the circle) is 3.14159265... a number known as Pi

  • The formula for circumference is C = 2πr C = 2 π r The formula for area of a circle is A =πr2 A = π r 2 Remember, that we approximate π π with 3.14 3.14 or 22 7 22 7 depending on whether the radius of the circle is given as a decimal or a fraction.
  • Problem 1: The diameter of a cart wheel is 2.1 m. Find the distance traveled when it completes 100 revolutions. Solution: In order to find the distance covered in one revolution, we have to find the circumference of the circle.
  • Microsoft Word - Problem Solving Circle.docx Created Date: 3:03:37 PM.

Pi (pronounced like 'pie') is often written using the greek symbol π

The definition of π is:

The Circumference
divided by the Diameter
of a Circle.

Circles And Anglesmath Problem Solving

The circumference divided by the diameter of a circle is always π, no matter how large or small the circle is!

To help you remember what π is ... just draw this diagram.

Finding Pi Yourself

Draw a circle, or use something circular like a plate.

Measure around the edge (the circumference):


I got 82 cm

Measure across the circle (the diameter):


I got 26 cm

Divide:

82 cm / 26 cm = 3.1538...

That is pretty close to π. Maybe if I measured more accurately?

Using Pi

We can use π to find a Circumference when we know the Diameter

Circumference = π × Diameter

Example: You walk around a circle which has a diameter of 100 m, how far have you walked?

= π × 100 m
= 314 m (to the nearest m)

Also we can use π to find a Diameter when we know the Circumference

Diameter = Circumference / π

Example: Sam measured 94 mm around the outside of a pipe ... what is its Diameter?

= 94 mm / π
= 30 mm (to the nearest mm)

Radius

The radius is half of the diameter, so we can also say:

For a circle with a radius of 1

The distance half way around the circle is π = 3.14159265...

Digits

π is approximately equal to:

Grade 2 Math Problem Solving

3.14159265358979323846…

The digits go on and on with no pattern.

π has been calculated to fifty trillion decimal places and still there is no pattern to the digits

Approximation

A quick and easy approximation for π is 22/7

22/7 = 3.1428571...

But as you can see, 22/7 is not exactly right. In fact π is not equal to the ratio of any two numbers, which makes it an irrational number.

A really good approximation, better than 1 part in 10 million, is:

355/113 = 3.1415929...
(think '113355', slash the middle '113/355', then flip '355/113')

Summary:

Circles And Anglesmath Problem Solving
22/7=3.1428571...
355/113=3.1415929...
π=3.14159265...

Remembering The Digits

I usually just remember '3.14159', but you can also count the letters of:

'May I have a large container of butter today'
3 1 4 1 5 9 2 6 5

To 100 Decimal Places

Here is π with the first 100 decimal places:

3.14159265358979323846264338327950288
4197169399375105820974944592307816
4062862089986280348253421170679...

Calculating Pi Yourself

There are many special methods used to calculate π and here is one you can try yourself: it is called the Nilakantha series (after an Indian mathematician who lived in the years 1444–1544).

Vertical Angles Problem Solving

It goes on for ever and has this pattern:

3 + 42×3×444×5×6 + 46×7×848×9×10 + ...

(Notice the + and pattern, and also the pattern of numbers below the lines.)

Steps In Math Problem Solving

It gives these results:

TermResult (to 12 decimals)
13
23.166666666667
33.133333333333
43.145238095238
...... etc! ...

Circles And Angles Math Problem Solving Worksheets

Get a calculator (or use a spreadsheet) and see if you can get better results.

Circles And Angles Math Problem Solving Solver

Pi Day

Pi Day is celebrated on March 14. March is the 3rd month, so it looks like 3/14