document.write( "Question 1199169: If y is inversely proportional to the cube of x, what percent does y change if x decreases by by 25%? \n" ); document.write( "

Algebra.Com's Answer #833118 by greenestamps(13203) $\"\"$ $\"About$

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\n" ); document.write( "While the responses from the other two tutors are fine, there is no need to use a formal proportion or to find the constant of proportionality, as they did in their responses. There is a much faster informal path to the answer.

\n" ); document.write( "The value of x decreases by 25% or 1/4, which means the new value is 3/4 of the old value.

\n" ); document.write( "Since the value of y is inversely proportional to the cube of x, the value of y changes by a factor of (4/3)^3 = 2.37 to 2 decimal places.

\n" ); document.write( "An increase by a factor of 2.37 means a percent increase of

\n" ); document.write( "100(2.37-1) = 100(1.37) = 137

\n" ); document.write( "ANSWER: y increases by 137% when x decreases by 25%

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