when you are answering questions on similar figures, you can
assume everything is similar. However, take note when you are
calculating area and volume.
when you have a 1cm by 1cm square, the area is 1*1=1cm2
but when you have a 2cm by 2cm square, the area is
2*2=2^2=4cm2
So when you are working on area (be it surface area), take the
power of 2.
In this question, ratio of big surface area: small surface
area=12^2:4^2=9:1
for length, just do what you always do for similar triangle.
height of large bottle/height of small bottle=circumference of
large bottle/circumference of small bottle
12/4=42/x
x=14cm