crystal 發問於 科學及數學數學 · 1 十年前

# F.3 VOLUME問2

1. Air is leaking out from a sherical balloon.Find the % decrease in its volume when its surface area has decreased by 36%.

2.It is known that nearly 70% of the surface of the Earth are oceans.

The radius of the Earth is 6400km.Find the total area of the oceans on the Earth.

PLZ show the steps.

### 1 個解答

• 1 十年前
最愛解答

1

let the radius of the original balloon is r1﹐the radius of the new balloon is r2

surface area has decreased by 36%

4*pi*r2^2=0.64*4*pi*r1^2

r2^2/r1^2=0.64

r2/r1=0.8

the volume of new balloon /the volume of original balloon

=(r2/r1)^3

=0.8^3

=0.512

so the % decrease of volume of new balloon

=1-0.512

=0.488

=48.8%

2

the radius of the Earth is 6400km

the surface area of the Earth

=4*pi*(6400)^2

=514719744 km^2

the total area of the oceans on the Earth.

=0.7*514719744 km^2

=360303820.8 km^2