above720 wrote:

Machine A and Machine B can produce 1 widget in 3 hours working together at their respective constant rates. If Machine A's speed were doubled, the two machines could produce 1 widget in 2 hours working together at their respective rates. How many hours does it currently take Machine A to produce 1 widget on its own?

a) 1/2

b) 2

c) 3

d) 5

e) 6

(E) it is

A = hours it takes machine A to produce 1 widget on its own

B = hours it takes machine B to produce 1 widget on its own

1/A + 1/B = 1/3

=> 3B + 3A = AB (1)

2/A + 1/B = 1/2

=> 4B + 2A = AB (2)

(1) & (2) => A = B

=> A = 6