If y varies inversely as x and y = 12 when x = 3, how do you find y when x = 4?

1 Answer
Apr 20, 2016

Answer:

#y=9# when #x=4#

Explanation:

If #y# varies inversely as #x# then
#color(white)("XXX")color(blue)(x) * color(red)(y)=c# for some constant #c#

Given #y=color(red)(12)# when #x=color(blue)(3)#
#color(white)("XXX")color(blue)(3) * color(red)(12) = c#

#color(white)("XXX")rArr c=36#

So
#color(white)("XXX")x * y = 36#
and when #x=color(green)(4)#
#color(white)("XXX")color(green)(4) * y = 36#

#color(white)("XXX")rArr y=9#