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Mar. 27Thursday, Day D

Mar. 27Thursday, Day D

(1) Take out your H.W.

(2) Copy and solve for x in notebook:

Activator:

2.3x =16.1

Calculate the ratio of circumference to diameter.

Discover the formula for the circumference of a circle and use it in solving circle problems.

Objective(s)

around across÷ = some #

around across = some #

circumference diameter 3.14

3.14circumference

diameter

or

÷ =

=

circumference diameter 3.14

3.14circumference

diameter

C

C

d

d

or

Which leads to the following formula for circumference…..

how?

Note:

Why did we use the ratio of circumference to diameter for several objects? Wouldn’t we have gotten the same result using just one object?

Why did we use the ratio of circumference to diameter for several objects? Wouldn’t we have gotten the same result using just one object?

Were any of the ratios in the last column not close to 3.14? If not, explain what might have happened.

Describe some situations in which knowing the circumference (and how to calculate it) would be useful.

Bike tires are often described by their diameter.

For instance, a 26-inch tire is a tire such that the diameter is 26". Each time the tire makes one complete rotation, the bike moves forward a distance equal to the circumference of the tire.

Therefore, it would be helpful to know how to calculate the circumference based on the diameter.