Train X and train Y pass one another traveling in opposite directions. Twenty minutes later they are 100 miles apart. If train X’s constant speed is 30 miles per hour greater than train Y’s, how far does train X travel during that time?  Choose the correct choice from the following answers.
A) 28  B) 40  C) 55  D) 72  E) 80
Let the rate of the Train Y be R   Then the rate of the Train X will be R+30 (given)   As per relative rate concept, the rate at which they are increasing the distance between them is R+(R+30) [add the rates] i.e. 2R+30   d=100 and t = 20 min i.e 20/60 hr   using RTD table, (2R+30) * 20/60 = 100 ==&gt; R= 135 miles/hr   So the rate of train X is 165 miles/hr (since R+30)   The distance traveled by Train X in 20 min is R*T = 165 * 20/60= 
<gadget id="calculator">165 * 20/60</gadget>
<output>55</output>
55 miles (55)
<result>C</result>
Train X and train Y pass one another traveling in opposite directions. Twenty minutes later they are 100 miles apart. If train X’s constant speed is 30 miles per hour greater than train Y’s, how far does train X travel during that time?