Quantitative Aptitude Free-Study Notes
6. AVERAGE
An average, or an arithmetic mean, is the sum of `n' different data divided by `n'
Average = Sum of Data / No. of Data
No. of Data = Sum of Data / Average
Sum of Data = Average * No. of Data
Points to remember:
1. Age of new entrant = New average + No. of old members x change in average
2. Age of one who left = New average - No. of old members x change in average
3. Age of new person = Age of the removed person + No. of members x change in average
In all the above three cases, if there is a decrease in the average, the sign of change in average will be negative.
4. If a certain distance is covered at x km/hr and the same distance is covered by y km/hr, then the average speed during the whole journey is 2xy / (x+y) km/hr.