Let x be the length of the garden
and y be the width of the garden.
since you only enclose 3 sides of the garden by a 40 ft fence. so the equation for this is:
2x + y = 40
and the area of the garden is 100 sq ft, so in equation
xy = 100
from equation 1, 2x + y = 40
y = 40 - 2x
substitute to equation 2
xy = 100
x ( 40 - 2x) = 100
40x - 2x^2 = 100
2x^2 - 40x + 100 = 0
x = 2.9 ft
y = 34.5 ft
We can use triangle inequality to prove it. What this rule is, it's basically if u add up 2 sides of the triangle, the length must be longer than the third side, check all 3 sides, and if all sides matches with the rule, a triangle is possible.
D, look it up on Math. Way it tells you mostly everything you can know about math.
Volume of a Cube = a³ ( a x a x a)
A = 8. 8³ = 8 x 8 x 8 = 512.
The cubes are one inch across so. 1 x 1 x 1 = 1.
512 x 0.25 = 128.
It would cost $128 to buy all the cubes.
Hope this helps!