If y varies directly as x and y=3 when x= 2, find y when x=8?

2 Answers
Jim G.
May 15, 2018

#y=12#

Explanation:

#"the initial statement is "ypropx#

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

#rArry=kx#

#"to find k use the given condition"#

#y=3" when "x=2#

#y=kxrArrk=y/x=3/2#

#"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(y=3/2x)color(white)(2/2)|)))#

#"when "x=8" then"#

#y=3/cancel(2)^1xxcancel(8)^4=3xx4=12#

Pallu
May 15, 2018

#y =12 # when #x = 8#

Explanation:

Given : #y# varies directly as #x#
#therefore x prop y#

#=> x = k y #, where #k# is constant of proportionality.

#=> y = x/k#--------(1)

When #x= 2, y = 3#

#=> 2 = k xx 3#

#=> k = 2/3#

#therefore# when x =8, (1) #=> y = 8/ (2/3)#

#=> y= 8 xx 3/2 = 4 xx 3 = 12#

# y =12#

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