Question

If y varies as x, and y is 20 when x is 4, what is the constant of variation for the relation?

Answer 1

y = kx
so
k = y/x

y is 20 when x is 4
k = 20/4 = 5

Answer
The constant of variation for the relation = 5

Answer 2

Hi there!

y ∝ x

∴ y = kx ---(i)
Where " k " is the constant of variation & k ≠ 0

Now to determine " k ".
Use the given condition that when :

• x = 4
• y = 20

Substitute th' respective values in Eqn. (i) :-

y = kx

⇒ 20 = k(4)

⇒ 4k = 20

⇒ k =
`\frac {20}{4}` = 5

Hence,
The constant of variation for the relation is 5

~ Hope it helps!