Question

The distance between two stations is 340 km. Two trains start simultaneously from these stations on parallel tracks to cross each other. The speed of one of them is greater than that of the other by 5 km/hr. If the distance between the two trains after 2 hours of their start is 30 km, find the sum of speed of both train.

• A. 138 km/hr
• B. 145 kn/hr
• C. 151 km/hr
• D. 155 km/hr

Answer 1

The correct option is D 155 km/hr

Distance between two stations = 340 km.

Let the speed of the first train = x km/hr.

Then speed of second train = (x + 5) km/h.

Time = 2 hours

Distance travelled by the first train in 2 hours = 2x km and distance travelled by the second train = 2(x + 5) km

According to the condition,

340 - [2(x + 5) + 2x] = 30 km

$\Rightarrow 340-(2x+10+2x)=30$

$\Rightarrow 4x+10=340-30$

$\Rightarrow 4x=340-30-10$

$\Rightarrow 4x=300$

$\Rightarrow x=\frac{300}{4}=75$

$\therefore$ Speed of first train = 75 km/hr and speed of second train = 75 + 5 = 80 km/ hr
So, sum of speed of both trains = 75 + 80 = 155 km/hr