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Grade 8 - Mathematics
2.13 Proportion - II

The circumference of a circle with a diameter of 4 meters is about 12.56 meters. A circle's circumference is proportional to its diameter. Write an equation relating the circumference of a circle to its diameter. What would be the circumference of a circle with a 5-inch diameter?
The constant of proportionality between circumference and diameter
12.56/4 = 3.14

The circumference is about 3.14 times the diameter.
Let C = circumference and d = diameter.
C = 3.14d = 3.14(5) = 15.7
The circumference is about 15.7 inches

Directions: Choose the correct answer. Also write at least 5 examples of your own.
Q 1: 7:5 = 49:30, are they in proportion?

Q 2: John sells 6 ounces chocolate for $2.70, how much does she charge for 10 pounds of chocolate?

Q 3: 2:5 = 10:25, are they in proportion?

Q 4: Find the missing quantity of the proportion in 7:__ = 21:24.

Question 5: This question is available to subscribers only!

Question 6: This question is available to subscribers only!

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