Answer 1

1 metre = `1/1000` km 

15 metre  = `15/1000` km 

1 second  = `1/3600` hr 

Here , Distance  = `15/1000` km 

Time taken = `1/3600` hr . 

Speed = `"Distance"/ "Time taken" `

         = `(15/1000)/(1/3600)`

         = `15/1000 × 3600/1`

         = 54 km `"h"^-1`