Question

В семье петровых девять детей и двое родителей. Средний возраст всех детей составляет 6 лет, а средний возраст всех членов семьи - 12 лет. Каков средний возраст родителей?

Answer 1

(9*6+2*х)/(9+2)=12
(54+2х)/11=12
54+2х=12*11
54+2х=132
2х=132-54
2х=78
х=78:2=39 лет

Answer 2

Calculation of the Average Age

To find the average age of the parents in the Petrov family, we can use the given information.

The family consists of nine children and two parents. The average age of all the children is 6 years, and the average age of all the family members is 12 years.

Let's denote the average age of the parents as P.

We can set up the following equation to find the average age of the parents:

(9 * 6 + 2 * P) / (9 + 2) = 12

Simplifying the equation, we get:

(54 + 2P) / 11 = 12

Multiplying both sides of the equation by 11, we have:

54 + 2P = 132

Subtracting 54 from both sides of the equation, we get:

2P = 78

Dividing both sides of the equation by 2, we find:

P = 39

Therefore, the average age of the parents in the Petrov family is 39 years.