Maths Olympiad Prep

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Algebra Difficulty 5.0 AIME Find the answer

Three real numbers x,y, x, y, and z z are such that (x+4)/2=(y+9)/(z3)=(x+5)/(z5) (x+4) / 2=(y+9) /(z-3)=(x+5) /(z-5) . Determine the value of x/y x / y .

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

Because the first and third fractions are equal, adding their numerators and denominators produces another fraction equal to the others: ((x+4)+(x+5))/(2+(z5))=(2x+9)/(z3) ((x+4)+(x+5)) /(2+(z-5))=(2 x+9) /(z-3) . Then y+9=2x+9 y+9=2 x+9 , etc.

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