The average of 25 results is 18 that of first 12 is14 and of the last 12 is 17 then the 13th number ಇಸ್
Answers
ANSWER"
The 13th number is 78
EXPLANATION:
Given that,
Total number of results = 25
Average = 18
Total results = x
Average = ----------------------------------
Total number of results
x
18 = ---------------------
25
x = 18 × 25
x = 450
Thus , Total result of 25 is 450 .
CASE 1 :
Number of results = 12
Average = 14
By formula
y
14 = ------------------
12
y = 14 x 12
y = 168
Thus ,Total result of first 12 is 168.
CASE 2 :
Number of results = 12
Average = 17
By formula ,
z
17 = ------------------
12
z = 17 × 12
z = 204
Thus , total result of last 12 is 204
.Therefore ,
13th number = Total results - Total results of first ' 12 - Total result of last 12
= x - y - z
= 450 - 168 - 204
= 4500 - 372
= 78