Let's denote the speed of the slower train as \( v \) kmph.

When two trains are moving in opposite directions, their relative speed is the sum of their individual speeds. Therefore, the relative speed of the two trains is \( v + 90 \) kmph.

To find the time taken for the trains to cross each other, we need to consider the combined length of the two trains, which is \( 1.10 \) km + \( 0.9 \) km = \( 2.00 \) km.

The time taken to cross each other is given as \( 47.99999999999999 \) seconds, which is approximately \( 48 \) seconds. However, we need to convert the speed from kmph to km/s to match the time unit of seconds.

We know that \( 1 \) kmph is equivalent to \( \frac{1}{3600} \) km/s (since there are \( 3600 \) seconds in an hour). Therefore, the relative speed in km/s is \( (v + 90) \times \frac{1}{3600} \).

Now, we can set up the equation using the formula \( \text{Distance} = \text{Speed} \times \text{Time} \):

\[ 2.00 \text{ km} = (v + 90) \times \frac{1}{3600} \text{ km/s} \times 48 \text{ s} \]

Solving for \( v \):

\[ 2.00 = (v + 90) \times \frac{48}{3600} \]

\[ 2.00 = (v + 90) \times \frac{4}{300} \]

\[ 2.00 = (v + 90) \times \frac{1}{75} \]

\[ 2.00 \times 75 = v + 90 \]

\[ 150 = v + 90 \]

\[ v = 150 - 90 \]

\[ v = 60 \]

Therefore, the speed of the slower train is \( 60 \) kmph.
느린 열차의 속도를 \( v \) kmph로 표시해 보겠습니다.

두 열차가 서로 반대 방향으로 움직일 때 상대 속도는 각 열차의 속도를 더한 값입니다. 따라서 두 열차의 상대 속도는 \( v + 90 \) kmph입니다.

두 열차가 서로 교차하는 데 걸리는 시간을 구하려면 두 열차의 합산 길이를 고려해야 하는데, 이는 \( 1.10 \) km + \( 0.9 \) km = \( 2.00 \) km입니다.

서로 교차하는 데 걸리는 시간은 \( 47.9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999