I think is 2.5 centimeters
Answer:
The diameter decreases at a rate of 0.143cm/min when it is of 10 cm.
Step-by-step explanation:
Surface area of an snowball:
An snowball has spherical format. The surface area of an sphere is given by:

In which d is the diameter of the sphere.
In this question:
We need to differentiate S implicitly in function of time. So

Surface area decreases at a rate of 9 cm2/min
This means that 
At which the diameter decreases when the diameter is 10 cm?
This is
when
. So




Area in cm², so diameter in cm.
The diameter decreases at a rate of 0.143cm/min when it is of 10 cm.
Use the Pythagorean theorem:
2)

4)

If you angle at the bottom is 50 that makes the opposite one 50 to and when there is a small square like at the top angle it means it is a 90° angle.
Since every triangle equals 180° you subtract 140 which is the 2 angles added together and the last angle would be 40°.