If Dev works alone he will take 20 more hours to complete a task than if he worked with Tina to complete the task. If Tina works alone, she will take 5 more hours to complete the complete the task, then if she worked with Dev to complete the task? What is the ratio of the time taken by Dev to that taken by Tina if each of them worked alone to complete the task?
Pick
A) 4 : 1	B) 2 : 1	C) 10 : 1	D) 3 : 1	E) 1 : 2

Rationale: let time taken by dev to complete the work alone be x days and that by tina be y days work done by dev in 1 day = 1 / x work done by tina in 1 day = 1 / y work done by devtina in 1 day = 1 / x + 1 / y = ( x + y ) / xy thus working together they will complete the work in xy / ( x + y ) days acc . to the ques : 1 ) if dev works alone he will take 20 more hours to complete a task than if he worked with tina ' x - xy / ( x + y ) = 20 = > ( x ^ 2 ) / ( x + y ) = 20 . . . . . . . . . . . . . ( i ) 2 ) if tina works alone , she will take 5 more hours to complete the complete the task , then if she worked with dev y - xy / ( x + y ) = 5 = > ( y ^ 2 ) / ( x + y ) = 5 . . . . . . . . . . . . . . ( ii ) dividing ( i ) by ( ii ) x ^ 2 / y ^ 2 = 4 = > x / y = 2 ans : b hope it helps
Answer: B