The circumference of a circle varies directly as its diameter. When the diameter of a circle is 6 inches the circumference is 18.84 inches then the diameter of a circle with circumference of 6.28 is?

The diameter is 2

Step-by-step explanation:

We can use a ratio to solve

6              x

 =

18.84      6.28

Using cross products

6 * 6.28 = 18.84x

Divide each side by 18.84

37.68/18.84 = x

2 =x

hello from mrbilldoesmath!

answer:

(7 x + 6 y) (49 x^2 - 42 x y + 36 y^2)

discussion:

the trick is to recognize that 343 = 7^3 and 216 = 6^3 and, in general,

a^3 + b^3 =   (a + b) (a^2 - a b + b^2).

in our case

343x^3+216y^3   =   (7x)^3 + (6y)^3

so take a = 7x and b = 6y in the above equation to get the answer.

you,

mrb