Let the speed of Y be Vkm∕h Time is taken by X to travel 30km=(30∕v)hr Time taken by X to travel 30km with doubled speed =30∕2v=(15∕v)hr Total time difference then the actual =3+2=5hr According to the statement, 30∕v−15∕v=5 ⇒15∕V=5 ⇒v=3km∕h So, the time is taken by X to travel 30km=30∕3=10 hours Time taken by Q to travel 30km=10−3=7 hours Speed of Y= distance ∕ time =30∕7=4