A company has two models of computers, model X and model Y. Operating at a constant rate, a model X computer can complete a certain task in 60 minutes and a model Y computer can complete the same task in 30 minutes. If the company used the same number of each model of computer to complete the task in 1 minute, how many model X computers were used?
Answers.
A) 18	B) 16	C) 15	D) 17	E) 20

Rationale: "let ' s say 1 work is processing 60 gb of data . model x : 1 gb per min model y : 2 gb per min working together , 1 x and 1 y = 3 gb per min so , 20 times as many computers would work at 60 gb per min . so no . of x = 20 answer is e"
Answer: E