Question

Please help me I need help

If the diameter of a circle is doubled, the circumference of the new circle is..
A. 1/4 of the circumference of the original circle
B. 1/2 of the circumference of the original circle
C. The same as the circumference as the original circle
D. 2 times the circumference of the original circle
E. 4 times the circumference of the original circle

Answer 1

D. 2 times the circumference of the original circle

Explanation:

The circumference of a circle is represented by the formula C = 2(r)pi (where is r is the radius), which can also be written as C = (d)pi, where d is the diameter, (since 2r is equivalent to d). If the diameter is doubled, the original equation can be rewritten as C = 2(d)pi. Therefore, the circumference of the new circle is double the original circle.

You can plug in a sample number to further prove this point. Pretend r = 3 so d = 6. C = 6pi. Now when the diameter is doubled, d = 12 and C = 12pi which is double 6pi.

So the answer is D. 2 times the circumference of the original circle

Answer 2

D

Explanation:

Let's call the original diameter x. Then, the circumference would be xπ. If the diameter is 2x, the circumference is 2xπ. 2xπ / xπ = 2 so the answer is D.