If x varies inversely as y and x = 20 when y = 600, find y when x = 400.
If x varies inversely as y.
∴ xy = k(constant) …(i)
If x = 20 and y = 600
∴xy = 20× 600 = 12000
⇒ k = 12000
When x = 400, then from Eq. (i)
y× 400 = k
⇒ y × 400 = 12000
⇒ 
63
If x varies inversely as y and x = 20 when y = 600, find y when x = 400.
If x varies inversely as y.
∴ xy = k(constant) …(i)
If x = 20 and y = 600
∴xy = 20× 600 = 12000
⇒ k = 12000
When x = 400, then from Eq. (i)
y× 400 = k
⇒ y × 400 = 12000
⇒