A train takes 3 hours less time for a journey of 360 km, if its speed is increased by 10 km/hr from its usual speed. What is its increased speed (in km/hr)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 40
Let the speed of train be x
According to question,
(360/x) - {360/(x + 10)} = 3
(360x + 3600 - 360x)/x2 + 10x = 3
3600 = 3x2 + 30x
x2 + 10x - 1200 = 0
By solving this x = 30
Increased speed = 30 + 10 = 40kmph