Put the given information into the formula and solve for the variable of interest.
.. V = π*r^2*h
.. 252π = π*r^2*7
.. (252π)/(7π) = r^2
.. 36 = r^2
.. 6 = r
The radius is 6 cm. Selection D is appropriate.
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We would prefer that the offered selections had the appropriate cm units attached.