Question

Question 63

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

Answer 1

If x varies inversely as y.
$\therefore$ xy = k (constant)...(i)
If x = 20 and y = 600
$\therefore xy=20\times 600=12000\Rightarrow k=12000$

When x =400, then from Eq (i).
$y\times 400=k$
$\Rightarrow y\times 400=12000$ [Putting the value of k]
$\Rightarrow y=\frac{12000}{400}=30$