Trains A and B are moving in opposite directions. Their speeds are in a ratio of 5:3, meaning Train A's speed is five times a constant factor (5x) and Train B's speed is three times the same constant factor (3x).
Let \( L_a \) denote the length of Train A, and \( L_b \) denote the length of Train B.
When the front ends of the trains meet, their relative speed is the sum of their individual speeds. Given the speed ratio of 5:3, the relative speed is:
\[ \text{Relative speed} = 5x + 3x = 8x \] where \( x \) is the constant factor.
The front of Train A passes the rear of Train B 46 seconds after their fronts met. The distance Train A's front travels relative to Train B during this period is the length of Train B, \( L_b \). This takes 46 seconds:
\[ L_b = \text{Relative speed} \times \text{Time} = (8x) \times 46 = 368x \]
An additional 69 seconds elapse from the moment the front of Train A passes the rear of Train B until their rears pass each other. The distance covered by the front of Train A relative to the rear of Train B during this time is the length of Train A, \( L_a \). This takes 69 seconds:
\[ L_a = \text{Relative speed} \times \text{Time} = (8x) \times 69 = 552x \]
The ratio of the lengths can be found by dividing the distance covered in Step 3 by the distance covered in Step 2:
\[ \frac{L_a}{L_b} = \frac{552x}{368x} \] Simplifying the expression yields:
\[ \frac{L_a}{L_b} = \frac{552}{368} = \frac{3}{2} \]
The ratio of the length of Train A to the length of Train B is 3:2.