a) 100 meters
b) 150 meters
c) 180 meters
d) 200 meters
Answer: d
Explanation: Let the length of the train be x meters and its speed be y m/sec.
Then, $$\frac{{\text{x}}}{{\text{y}}}$$ = 20
⇒ y = $$\frac{{\text{x}}}{{20}}$$
$$\frac{{{\text{x}} + 100}}{{30}}$$ = $$\frac{{\text{x}}}{{20}}$$
30x = 20x + 2000
10x = 2000
x = 200 meters
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