14.  Is  a  cube  a  right  prism?     Why?     Is  a  rectangular
solid  a  right  prism?     Why?

15.  What  is  the  volume  of  a  regular  four-sided  prism  if
the  height  is  6  in.  and  one  side  of  the  base  is  2  in.  ?     What
would  be  the  volume  if  the  height  were  doubled?  if  the  side
of  the  base  were  doubled  ?  if  both  were  doubled  ?

16.  The  bases  of  a  prism  are  trapezoids  whose  parallel
sides  are  12  ft.  and  8  ft.,  and  the  altitude  is  6  ft.     Find  the
volume  of  the  prism  if  the  height  is  32  ft.
17.  How  many  cubic  feet  of  stone  are  required  to  build  a
dam  1000  ft.  long,  20  ft.  high,  10  ft.  wide  at  the  bottom,  and
4  ft.  wide  at  the  top?    (Consider  the  dam  to  be  a  trapezoidal
prism  like  that  in  No.  16.)

18.  The  distance  around  a  reservoir  in  the  shape  of  a
regular  hexagon  is  360  ft.     If  the  average  daily  loss  from
evaporation  amounts  to  a  layer  of  water  2   in.   deep,   how
many  cubic  feet  of  water  must  be  supplied  daily  to  maintain
the  water  at  a  constant  level  ?

19.  Pencils  are  often  made  in  the  shape  of  regular  hexa-
gonal prisms.     Find  the  volume  of  the  pencil  given  you  (cor-
rect to  a  hundredth  of  a  cubic  inch).
164


LESSONS   IN  GEOMETRY.
Lesson  88.
1.  Define  a  right  cylinder,  and  the  related  terms.
A  right  cylinder  is  the  solid  generated   by  a  rectangle

revolving  about  one  of  its  sides.
A  right  cylinder  is  also  called  a  cylinder  of  revolution.
