# Paint and weather balloon

mary d
You launch a group of helium filled spherical weather balloons which have been painted with a thin layer of signal reflecting paint. the first balloon requires 2.75 liters of paint the second balloon you launch is bigger it's diameter is bigger by a factor of 2.75 how much paint will be needed for the second balloon. where do I start with this problem? is there a formula somewhere?

## Answers and Replies

the equation for the area of a sphere is
a=4*pi*(r^2)
suppose that a is the area of the first balloon
Now to calculate tha area of the second balloon (a2) put
a2=4*pi*((r*2.75)^2)
=4*pi*(r^2)*7.56
As you can see, the area of the second balloon is bigger than of the first by a factor of 7.56
The quantity of paint you need to paint a balloon is proportional to the area of the balloon

HallsofIvy
Science Advisor
Homework Helper
The quantity of paint you need to paint a balloon is proportional to the area of the balloon.

And that is proportional to the square of the diameter.
Since the second balloon's diameter is 2.75 times as big, you will need (2.75)2= 7.5625 times as much paint, just as meteor said.