Working individually, Jane can bake cakes for 4 hours and Roy can bake cakes in 5 hours. If Jane and Roy work together but independently at the task for 2 hours, at which point Roy leaves, how many remaining hours will it take Jane to complete the task alone? Answers.
A) 1/2  B) 2/5  C) 3/4  D) 1/4  E) 1/5
In first 2 hrs Roy will finish 2/5 = 2/5 of work and Jane will finish 2/4 work so total 2/5 + 1/2 = 9/10 work is finished and 1-9/10 = 1/10 work remaining. Now Jane will take (1/10)*4 = 2/5 hrs to finish it.   So answer is 2/5.
<result>B</result>
Working individually, Jane can bake cakes for 4 hours and Roy can bake cakes in 5 hours. If Jane and Roy work together but independently at the task for 2 hours, at which point Roy leaves, how many remaining hours will it take Jane to complete the task alone?