Aptitude

In a college the number of students studying Arts, Commerce and Science are in the ratio of 3:5:8 respectively. If the number of students studying Arts, Commerce and Science is increased by 20%, 40%, and 25% respectively, what will be the new ratio of students in Arts, Commerce and Science respectively?

A boat running downstreams covers a distance of 30 kms in 2 hours. While coming back the boat takes 6 hours to cover the same distance. If the speed  of the current is half that of the boat, what is the speed of that boat in kmph?

If 4x+5y=83 and $$ \ {3x\over2y}={21\over22}$$then what is the value of y-x ?

A 160-meter-long train running at a speed of 90 km/h crosses a platform is 18 s. What is the length of the platform in metre?