Question

x varies inversely as y, when x = 15 then y = 10, if x = 20 then y = ?

Answer 1

It is given that x varies inversely as y, i.e., `x  α  1/y`

∴ \[x = \frac{k}{y}\] , where k is constant of variation
⇒ x × y = k

When x = 15, y = 10.

∴ k = 15 × 10 = 150

So, the equation of variation is xy = 150.

When x = 20,

20y = 150

⇒ y = \[\frac{150}{20}\]

y = 7.5