Question

y varies inversely with x. if y = 30 when x = 12 , find y when x = 15​

Answer 1

Step-by-step explanation:

yx=k

k=30×12=360

in second case

y15=360

So y=360/15

y=24

Answer 2

Given that,  y ∝ (1/x) ∴ y = k x (1/x) where, k is the constant of variation.  ∴ y × x = k …(i)  When x = 12, y = 30 ∴ Substituting, x = 12 and y = 30 in (i), we get y × x = k  ∴ 30 × 12 = k  ∴ k = 360  Substituting, k = 360 in (i), we get y × x = k  ∴ y × x = 360 ….(ii)  i. When x = 15,y = ?  ∴ Substituting x = 15 in (ii), we get y × x = 360  ∴ y × 15 = 360 y = 360/15 y = 24 ii. When y = 18, x = ?  ∴ Substituting y = 18 in (ii), we get y × x = 360  ∴ 18 × x = 360 x = 360/18 x = 20Read more on Sarthaks.com - https://www.sarthaks.com/855158/y-varies-inversely-with-x-if-y-30-when-x-12-find-i-y-when-x-15-ii-x-when-y-18