The average of 12 numbers is 42. If average of first 4 numbers is 44 and average of last 5 numbers is 40. If 6th number is 6 less than 5th number and 5 less than 7th number find sum of 5th and 7th number.
Answers
Answer:
89
Step-by-step explanation:
formula of average is =
( sum of all observations) / number of observations
according to question , we have 12 observations & their average is 42
so,
sum of all observations = 42×12 => 504
similarly
sum of first 4 observations = 44×4 => 176
sum of last 5 observations = 40×5 => 200
now we having 3 observations left ie 5th, 6th, 7th
according to question
let 6th observation is x
5th observation will be (x+6)
7th observation will be (x+5)
sum of 5th, 6th, 7th observations = 128
x+ (x+6) + (x+5) = 128
3x + 11= 128
3x = 128-11
x = 117/3
x = 39
5th observation is 45
6th observation is 39
7th observation is 44
so, sum of 5th and 7th observations are
45 +44 = 89
{ because ,sum of 12 observations - sum of first 4 and last 5th observations = 128
504-(176+200) = 128 }
Answer:
Step-by-step explanation:
