Train A passes a bridge in 20 seconds and a pole in 15 seconds then what is the value of "p" if ratio between length of the bridge and train A is 5 : (p + 4)?

Train A passes a bridge in 20 seconds and a pole in 15 seconds then what is the value of "p" if ratio between length of the bridge and train A is 5 : (p + 4)? Correct Answer 11

Given:

Train passes bridge in 20 seconds

Concept:

Speed = Distance/Time

Calculation:

Let be assume distance of the bridge is 5x and train is 4x and speed of train is S

⇒ S = (p + 4)x/15         ....(1)

⇒ S = (p + 4 + 5)x/20         ....(2)

⇒ (p + 4)x/15 = (p + 9)x/20

⇒ 20p + 80 = 15p + 135

⇒ 5p = 55

⇒ p = 11

∴ The required result will be 11.