The statement that y = 4 when x = 4, z = 20, and w= 4 is not true because the constant of proportionality is not equals to 2 / 5.
What is variation?
Variation describes a simple relationship between two variables.
Therefore, y varies jointly as x and z and inversely as the square of w
y ∝ xz ∝ 1 / w²
Therefore,
y = kxz / w²
where
k = constant of proportionality
Hence,
y = 3
x = 3
z = 10
w = 2
yw² / xz = k
k = 3 × 2² / 3 × 10
k = 12 / 30
k = 6 / 15 = 2 / 5
Therefore, let's test for y = 4 when x = 4, z = 20, and w= 4.
k = 4 × 4² / 4 × 20
k = 64 / 80
k = 16 / 20 = 4 / 5
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