Average

1..A train runs 3 hours at a speed of 65 km per hour and for next 2 hours at a speed of 70 km per hour. Find the average speed of the train for the 5 hours' journey.

solution: Total distance covered in first 3 hours: (65*3)      = 195 km
             Total distance covered in next 2 hours: (70*2)      = 140 km
             Total distance covered in first 5 hours: (195+140) = 335 km

  so, Average speed for 5 hours' journey= 335/5= 67 km/hr.


2..Find the average of 7 numbers if the sum of the first four is 76 and the sum of the last three s 78.


Solution:  Sum of first four numbers = 76
               Sum of last seven numbers = 78
               Total of seven numbers= 76+78=154
         
              So, Average of 7 numbers = 154/7= 22