If y varies inversely as x, and y=10 when x=4, how do you find x when y=8?

2 Answers
Binayaka C.
Nov 19, 2017

#x=5#

Explanation:

#y prop 1/x :. y=k*1/x :. x*y =k ; #

When #x=4 ; y=10 :. 4*10=k or k=40 #.

So variation equation is #x*y =40 #

When #y=8 ; x=40/8=5 :. x=5# [Ans]

Jim G.
Nov 19, 2017

#x=5#

Explanation:

#"the initial statement is "yprop1/x#

#"to convert to an equation multiply by k the constant"#
#"of variation"#

#rArry=kxx1/x=k/x#

#"to find k use the given condition"#

#y=10" when "x=4#

#y=k/xrArrk=yx=10xx4=40#

#"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(y=40/x)color(white)(2/2)|)))#

#"when " y=8#

#x=40/y=40/8=5#

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