application word problem

Question

One printing press can print the first edition of a book in 66 min. A second printing press requires 55 min to print the same number of copies. How long would it take to print the first edition of the book with both presses operating?

Answer 1

1/66+1/55 = 1/t

multiply by 330t

5t+6t = 330

11t =330

t= 330/11

t= 30 hours