Answer:

Step-by-step explanation:
Recall that the volume of a whole sphere is given by the formula:

then, the volume of a semi-sphere would be half of the formula above:

Now, the radius R is given by half of the semi-sphere diameter: 15/2 = 7.5 cm.
which makes our calculation:

Answer:
the question is nonstatistical.
A.)Rachel should have 6 second class tramps. Because if you do the equation 6+6+6 you get 18 (the number of first class stamps she has)
2.)Add 6 to 18 to get your answer :)
He had 20 questions to answer hope it helps