Machine A and machine B are each used to manufacture 220 sprockets. It takes machine A 10 hours longer to produce 220 sprockets than machine B. Machine B produces 10 percent more sprockets per hour than machine A. How many sprockets per hour does machine A produces? Answers
A) 2
B) 3
C) 4
D) 5
E) 6

Rationale: "machine b : takes x hours to produce 220 sprockets machine a : takes ( x + 10 ) hours to produce 220 sprockets machine b : in 1 hour , b makes 220 / x sprockets machine a : in 1 hour , a makes 220 / ( x + 10 ) sprockets equating : 1.1 ( 220 / ( x + 10 ) ) = 220 / x 242 / ( x + 10 ) = 220 / x 242 x = 220 x + 2200 22 x = 2200 x = 100 a makes 220 / ( 110 ) = 2 sprockets per hour answer : a"
Answer: A