Correct Answer - Option 2 : 90 km/hr
Given:
speed of the slower train = 60 km/hr
Formula:
Ratio of their speed (1st train to 2nd train) = √t2/√ t1
Where, t2 = time taken by 2nd train covers its remaining journey
t1 = time taken by 1st train covers its remaining journey
Percentage = (new value/original value) × 100
Calculation:
Time taken by 2nd train cover its journey after meeting = (225/100) × 4 = 9 hrs
\(\Rightarrow \frac{{speed\;of\;faster\;train}}{{speed\;of\;slower\;train}} = \frac{{\sqrt 9 }}{{\sqrt 4 }} = \frac{3}{2}\;\)
∴ The speed of the faster train = 3/2 × 60 = 90 km/hr