Question

A car travels with a speed of 30 km/h in fist second , with 40km/h in next two seconds and with 50 km/h in next three seconds .Find the average speed of the car .

Answer 1

we know ,
 average speed  = total distance / total time taken
   now,
total distance = 30 km/h *1sec + 40 km/h*2sec + 50 km/h*3sec
                        =5/18{ 30 + 40*2 + 50*3} m
                        =5*260/18 m =1300/18 m
  
total time taken = 1sec + 2sec + 3sec = 6 sec

average speed = 1300/6*18 = 1300/108 m/sec =12m/sec