New Average when a person leaves the group
Rule 1:
In case of increase in average
Age of leaving member = Previous average - ( Increase in average × Number of members excluding leaving member)
The average weight of 10 mangos in the box is 450 grams. But accidentally one mango fell away out of the box resulting in increase of the average weight by 10 grams. What is the weight of that mango?
Sol:
Age of leaving member = Previous average - ( Increase in average × Number of members excluding leaving member)
Previous average = 450 grams
Increase in average = 10 grams
Number of members excluding leaving member = 9
Age of leaving member = 450 – (10 × 9) = 450 – 90 = 360 grams.
Rule 2:
In case of decrease in average
Age of leaving member = Previous average + ( Decrease in average × Number of members excluding leaving member)
The average height of 10 boys is 165 cm. But one boy leaves the class and as a result there is a decrease in average height by 2 cm. What is height of leaving boy?
Sol:
Age of leaving member = Previous average + ( Decrease in average × Number of members excluding leaving member)
Previous average = 165 cm
Decrease in average = 2 cm
Number of members excluding leaving member = 9
Age of leaving member = 165 + ( 2 × 9) = 165 + 18 = 183 cm
Rule 3:
New average of group =
A group of 10 persons has average age of 30 years. A person aged 40 years left the group. What is new average of the group?
Sol:
New average of group =
Previous average = 30 years
Number of persons including leaving person = 10
Age of leaving member = 40 years
Number of members excluding leaving member = 9
