6.6 Around the World
Example 1: If the diameter of the earth is 8,000 miles, find the average speed in miles per
hour Phileas Fogg needs to circumnavigate the earth about the equator in 80 days.
𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒
(𝑠𝑝𝑒𝑒𝑑 =
)
𝑡𝑖𝑚𝑒
Example 2: An audio CD spins at a rate of 200 rotations per minute. If the radius of a CD is 6
cm, how far does a point on the outer edge travel during the playing of a 57-minute CD?
Example 3: The wheel on Chad’s unicycle has a diameter of 26 feet.
a) How far will the unicycle travel in 100 revolutions of the wheel? Give your answer to
the nearest whole foot.
b) Chad rides his unicycle 4 miles to school each day. About how many revolutions does
the wheel make during his trip? (5,280 ft = 1 mile)
LESSON 6.6 AROUND THE WORLD
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Example 4: Use 3.14 for π and round to the nearest tenth of a centimeter.
a) The needle of the scale in the bulk food section of a supermarket is 24 cm long. What
distance does the top of the needle travel when it rotates 980°?
b) The needle of the scale in the bulk food section of a supermarket is 32 m long. What
distance does the top of the needle travel when it rotates 350°?
Example 5: Round to the nearest tenth.
a) A pizza 10 inches in diameter is shared by three people in the ratio of 1:3:4 pieces.
What is the length of the crust for each of the three portions?
b) A pizza 6 inches in diameter is shared by three people in the ratio of 1:4:5 pieces.
What is the length of the crust for each of the three people?
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Example 6: Given the problem, find the diameter using the provided information.
a) To find the diameter of a pillar, Kate wraps a 14 foot rope around its base. She finds
that the rope wraps around the base exactly 2 times. What is the diameter of the pillar
to the nearest tenth?
b) To find the diameter of a tree, John wraps a 26 foot rope around its base. He finds
that the rope wraps around the base exactly 4 times. What is the diameter of the three
to the nearest tenth?
Example 7:
a) Mike times his box car as it goes around circular track and clocks it at 34 seconds per
revolution. If the radius of the track is 64 inches, what is the speed of the train in
inches per second?
b) Kim times her dog as it runs around a circular track and clocks it at 50 seconds per
revolution. If the diameter of the track is 85 inches, what is the speed of the dog in
inches per second?
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Example 8:
a) Kelly watched a bug crawl through an arc of 25° along the rim of half a melon. If the
radius of the melon was 3 inches, how far did the bug crawl?
b) Felix watched a snail crawl through an arc of 10° along the rim of half an orange. If
the radius of the orange was 6 inches, how far did the snail crawl?
HOMEWORK: PP. 338 # 1 - 6
LESSON 6.6 AROUND THE WORLD
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