The ratio between the speeds of two trains is 7: 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is ?  Choose the correct choice from the following answers.
A) 83.5 km/hr B) 84.5 km/hr C) 86.5 km/hr D) 87.5 km/hr E) None of these
Explanation:   Let the speeds of two trains be 7X and 8X km/hr.   8/X=400/4=&gt;X=12.5Km/hr   So speed of first train is   12.5*7= 
<gadget id="calculator">  12.5*7</gadget>
<output>87.5</output>
87.5 km/hr   Option 87.5 km/hr
<result>D</result>
The ratio between the speeds of two trains is 7: 8. If the second train runs 400 kms in 4 hours, then the speed of the first train is ?