Question

If x varies inversely as y and x=20 when y=600,find y when x=400

Answer 1

x $\propto$ $\dfrac{1}{y}$

➾ xy = k (Where k is constant)

By putting the values,

➾ 20 × 600 = k

➾ k = 12000


When x = 400 and y = ?

xy = k (Where is constant)

By putting the values,

➾ 400 × y = 12000

➾ y = $\dfrac{12000}{400}$

➾ y = 30



∴ The value of y is 30




Verification :-

xy = k

➾ 400 × 30 = 12000

➾ 12000 = 12000

∴ LHS = RHS ✔✔

Answer 2

x=20 then y=600
x=400 then y=?
20- 600
400-?
y= (600×400)÷20
y=12000