Question

Is this correct?

Answer 1

@mathmate

Answer 2

the ratio of surface areas is the square of the ratio of their lengths.

in other words, square 4/7
(which means square the top, and square the bottom)

Answer 3

So c?

Answer 4

Yes, ratio of areas is the square of the ratio of linear dimensions.
An easy way to remember is if you put the units in there:
4 cm : 7 cm
\(4^2 cm^2 : 7^2 cm^2 = 16 cm^2 : 49 cm^2\)
Similarly, for ratio of volumes,
\( 4^3 cm^3 : 7^3 cm^3 = 64 cm^3 : 343 cm^3\)