Please help with geometry

a. 9902.77208 cm^3

b. 4601.38604 cm^3

c. 13 cm

Step-by-step explanation:

The equation to finding the volume of a balloon is V = (4/3)()(r^3)

If the diameter of the balloon is 26 cm, that means the radius of the balloon is 13 cm, since the radius is half the diameter. That means we can substitute 13 as r in the equation. If you do the math the volume of the first balloon is approximately 9902.77208 cm^3.

If the balloon is only half-inflated, that means its volume is half the original balloon. That means we can easily halve the volume from the first question. The half amount will turn out to be approximately 4601.38604 cm^3.

Since the ballon is half-inflated, the diameter is also half the original balloon. The original diameter was 26 cm, so the diameter of the new balloon will be 13 cm.  

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents