20 imperial gallons = 90.9218 litres
so i'd say you'd need to buy 91 bottles or...
20 US Liquid gallons = 75.7082 litres
so you'd have to buy 76 bottles.
Hope this answers your question! It depends what gallon you're working from.
See the diagram below.

is the height, and

is the slant height.
The height is the distance from the
base of the pyramid to the vertex (the top of the pyramid). It runs perpendicular to the base.
The slant height is the distance from the
base of the triangles which make up its sides to the vertex. It runs perpendicular to this base as well.
$68
divide 8 by 2 to get 4
multiply 17 times 4 to get 68
Step-by-step explanation:
1. Draw the bottom line EF with a ruler.
2. Use a protractor and draw 2 long lines at 50 degrees, one from point E and one from F and make sure the two lines intersect.
The correct answer:
The corresponding segments BC and AD in the image are parallel