Question

A man's age is 42 years and his son's age is 12 years. After how many years will the man be thrice as old as his son?

Answer 1

$Heya!!$


$\bf{Answer \ : \ - \ 3 \ years}$

Here is your solution : - 

Given ,

Man's present age = 42 years 

His son's present age = 12 years

To find ,

After how many years will the man's age be thrice of his son.

Main solution : -

Let after x years age of man will be thrice that of his son.

Man's age after x years = 42 + x

His son's age after x years = 12 + x

The condition is,

Man's age should be thrice of his son.

So, the linear equation framed is as follows : -

42 + x = 3 ( 12 + x )

Now, solving this equation for x using transposition.

The steps are as follows : -

=> Open the brackets on R.H.S

=> 42 + x = 36 + 3x

=> Transposing 42 to R.H.S and 3x to L.H.S

=> The signs will change while transposing.36

=> x - 3x = 36 - 42

=> -2x = -6

=> x = -6/-2

=> x = 3 years 

Hence , age of the man will be equal to thrice of his son after 3 years.

$\boxed{Hope \ it \ helps \ you \ : \ ) }$

Answer 2

$\textbf{Solution :-}$

$\textbf{Given that ,}$


□ The age of a man is = $\textbf{42 years}$

□ The age of his son = $\textbf{12 years}$


$\textbf{To solve =>}$

□ The years when will be the man as old as his son ❔


□ $\textbf{Let's solve ,}$

Suppose after $\textbf{" y " years}$ the age of the man will be thrice as old as his son.


$\textbf{According to the question ,}$

□ After " y " years the age of the man will be = $\textbf{42 + y}$

□ And his son's will be = $\textbf{12 + y}$

Now , compare the man's age with his son's age.

Thrice of his son's age = Man's age

=> 3 ( 12 + y ) = 42 + y

=> 36 + 3y = 42 + y

=> 3y - y = 42 - 36

=> 2y = 6

=> y = 3


Hence , after $\textbf{3 years}$ the age of the man will be as old as his son.


$\textbf{Let's prove ,}$

Put the value of 3 on above equation :-


$\textbf{i.e.}$

=> 3 ( 12 + y ) = 42 + y

=> 3 ( 12 + 3 ) = 42 + 3

=> 3 × 15 = 45

=> $\textbf{45 = 45}$

L.H.S. = R.H.S.



||||| $\textbf{Thanks}$ |||||

||||| $\textbf{be brainly}$ ||||| ☺