Question 987443
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y varies directly as {{{sqrt(x)}}}
x decreases 64%, leaving 36% of x.
{{{sqrt(.36x)=0.6sqrt(x)}}}
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For a 64% decrease in x, we get a 40% decrease in the square root of x.
So when y varies directly as the square root of x, for a 64% decrease in x we have a 40% decrease in y.
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CHECK: 
Select any values:
If x=100 then sqrt(x)=10, decreases by 64%, x=36 and sqrt(x)=6
Before, sqrt(x)=10, after sqrt(x)=6, a 40% decrease.
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If x=169 then sqrt(x)=13, decrease by 64%, x=60.84 and sqrt(x)=7.8 
Before, sqrt(x)=13, after sqrt(x)=7.8, a 40% decrease.
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If x=4 then sqrt(x)=2, decrease by 64%, x=1.44 and sqrt(x)=1.2
Before, sqrt(x)=2, after sqrt(x)=1.2, a 40% decrease.