Average shortcut formula

Average shortcut formula for solving avearge questions:




This can be modified in other formula like :

Number(change in average)=  Added- Removed





 Examples of the formula :
 1. The average of five numbers is 27. If one number is excluded, the average becomes 25. What is the excluded number?

Solution :  25=(27*5-x)/4
 Ans 35



 2.A student's mark was wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by 2 . What is the number of students in the class?
Ans
Using Modifed formula :
X*2=63-83
X=20/2=10  (ignore -ve sign)


 3. The average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What is the weight of the new person?
Ans 85
Solution:
8*2.5=x-65
X=65+20=85


 4. A batsman makes a score of 87 runs in the 17th inning and thus increases his averages by 3. What is his average after 17th inning?
Ans 39
Solution:
X+3=(16*x+87)/17
17x-16x=87-51
X=36
New average=36+3=39