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imc

algebra intermediate

Problem

Consider the set of all fractions , where and are relatively prime positive integers. How many of these fractions have the property that if both numerator and denominator are increased by , the value of the fraction is increased by ?
(A)
(B)
(C)
(D)
Solution
You can create the equation Cross multiplying and combining like terms gives . This can be factored into . and must be positive, so and , so and . Using the factors of 110, we can get the factor pairs: and But we can't stop here because and must be relatively prime. gives and . and are not relatively prime, so this doesn't work. gives and . This doesn't work. gives and . This does work. We found one valid solution so the answer is .
Final answer
B