The ratio between the speeds of two trains is 2:7. If the first train runs 350km in 2 hours, then the sum of the speeds (in km/h) of both the trains is:
- A750.5
- B775
- C787.5
- D780.5
Solution & Step-by-step Explanation
Let the speed of the first train be 2x and the second train be 7x.
Given that the first train travels 350km in 2 hours:
Speed of the first train=
Time
Distance
=
2
350
=175km/h
Now equate this to 2x:
2x=175⟹x=
2
175
=87.5
We need to find the sum of the speeds of both trains:
Sum of speeds=2x+7x=9x
Sum of speeds=9×87.5=787.5km/h
Given that the first train travels 350km in 2 hours:
Speed of the first train=
Time
Distance
=
2
350
=175km/h
Now equate this to 2x:
2x=175⟹x=
2
175
=87.5
We need to find the sum of the speeds of both trains:
Sum of speeds=2x+7x=9x
Sum of speeds=9×87.5=787.5km/h