Question

The average age of four children is 11 years if the age of three children are 9 years 12 years and 10 years find the age of fourth child

Answer 1

Given that:

• The average age of four children is 11 years.
• The age of three children are 9 years, 12 years and 10 years.

To Find:

• The age of fourth child.

Let us assume:

• The age of fourth child be x years.

We know that:

• Average age = Sum of ages / Number of children

We have:

• Average age = 11 years
• Sum of ages = 9 + 12 + 10 + x = (31 + x) years
• Number of children = 4

Finding the age of fourth child:

⟶ 11 = (31 + x) / 4

Cross multiplication.

⟶ 4(11) = 31 + x

⟶ 44 = 31 + x

⟶ 44 - 31 = x

⟶ 13 = x

⟶ x = 13

Hence,

• The age of fourth child is 13 years.

Answer 2

Given:-

• The average age of four children is 11 years

• the age of three children are 9 years 12 years and 10 years

To find:-

• find the age of fourth child

Solution:-

❍ Let the age of fourth child be x

Sum of ages=(9 + 12 + 10 + x)=(31 + x)

As we know that,

⠀⠀

⠀⠀$\boxed{\pink{\sf Average~age=\dfrac{Sum~of~ages}{Number~of~children}}}$

⠀⠀ ⠀According to the question,

⠀⠀

⠀⠀⠀⠀⠀${:\implies{\sf{11=\dfrac{31+x}{4}}}}$

⠀⠀⠀⠀⠀${:\implies{\sf{31+x=44}}}$

⠀⠀⠀⠀⠀${:\implies{\sf{x=44-31}}}}$

⠀⠀⠀⠀⠀${:\implies{\sf{\purple{x=13}}}}$

$\therefore{\underline{\textsf{Hence, the~age~of~fourth~child~is~\textbf{13}}}}$

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