lean_workbook_plus_71314

Train A passes a milestone in 8 seconds before meeting train B. The two trains pass each other in 9 seconds. Then train B passes the same milestone in 12 seconds.\n\nWhich of the following statements about the lengths of the trains is true?\n\na, A is twice as long as B\nb, A and B are of equal length\nc, B is 50% longer than A\nd, B is twice as long as A\ne, cannot be deducted about the length of A and B\n\nAssume that Train A's length to be $x$ and it's speed $a$ , and Train B's, $y$ and $b$ , respectively.\n\nFrom the question, we know that\n\n$x=8a$ (i)\n\n$y=12b$\n\n$\frac{x+y}{a+b}= 9$\n\n\nThen, we have $x+y=9a+9b \to 8a+12b=9a+9b \to 3b=a$\n\nSubstituing the latter into (i), we get $x=24b=2y$