Question

the average age of 3 sisters is 15. the ages of 2 sisters are 12 and 15
the age of the third sister is?
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Answer 1

Answer : 18 years

Explanation :

Given :

The average of 3 sisters = 15

The ages of two sisters = 12 and 15

let the age of third sister be x

Mean = Sum of all observations/ Number of observations

According to the problem,

15 = (12 + 15 + x) / 3

15 = (27 + x) / 3

15 × 3 = 27 + x

45 = 27 + x

x = 45 - 27

x = 18

Therefore, the age of third sister is 18 years.

Answer 2

Answer: 18 years is the answer

Step-by-step explanation:

because the avg age is 15 years so let the age of third sister be x . x +12+15=45

x+27 = 45

x=45-27 =18.