document.write( "Question 828151: Suppose that x varies directly as z and that y also varies directly as z.\r
\n" ); document.write( "\n" ); document.write( "(A) does x + y vary directly as as z?
\n" ); document.write( "(B) does xy vary directly as z?
\n" ); document.write( "(C) does sqrt(xy) vary directly as z? Assume x, y and z are positive.\r
\n" ); document.write( "\n" ); document.write( "The answers are yes, no, yes respectively.\r
\n" ); document.write( "\n" ); document.write( "I don't really understand why the answer isn't 'yes' for all the questions. I'm thinking that the formula I should work with is z = kxy. Could you please explain to me these answers? Thank you in advance.
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Algebra.Com's Answer #499070 by Alan3354(69443)\"\" \"About 
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Suppose that x varies directly as z and that y also varies directly as z.\r
\n" ); document.write( "\n" ); document.write( "(A) does x + y vary directly as as z?
\n" ); document.write( "(B) does xy vary directly as z?
\n" ); document.write( "(C) does sqrt(xy) vary directly as z? Assume x, y and z are positive.\r
\n" ); document.write( "\n" ); document.write( "The answers are yes, no, yes respectively.\r
\n" ); document.write( "\n" ); document.write( "I don't really understand why the answer isn't 'yes' for all the questions. I'm thinking that the formula I should work with is z = kxy.
\n" ); document.write( "-----------------
\n" ); document.write( "For B, xy varies \"directly\" as z in the sense that when z increases xy increases.
\n" ); document.write( "But, since xy is a product it varies as the square of z.
\n" ); document.write( "If z is doubled, both x and y are doubled --> xy is 4 times.
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