Correct Answer - Option 4 : 5000 metres
Given:
The speed of the boy = 20 km\h
Formula used:
\(S\ =\ {D\over T}\) (Where S = Speed, D = Distance, and T = Time)
Calculation:
Let us assume the length of the bridge be X
⇒ The speed of the boy = 20 × (5/18) = 100/18 m/s
⇒ The time = 15 minutes = 15 × 60 = 900 seconds
⇒ X = \({900}\ \times {100\over 18}\) = 5000 metres
∴ The required result will be 5000 metres.