Question

Illa
5. The present age of two brothers are in the ratio of 3 : 4. Five years back their ages were in the
ratio of 5 : 7. Find their present ages.
[Ans. 30 years and 40 years]
​

Answer 1

Answer:

Step-by-step explanation:

let the ratio be X.

then ages will be 3x and 4x.

5years later, younger boy age=3x-5

elder boy age=4x-5

now, a/q

3x-5/4x-5=5/7

7(3x-5)=5(4x-5)

21x-35=20x-25

21x-20x= -25+35

X=10years

younger boy age=3x=3*10=30

elder boy age =4x=4*10=40

Answer 2

Given :

The present age of two brothers are in the ratio of 3 : 4. Five years back their ages were in the ratio of 5 : 7.

To Find :

Their Present Ages.

Solution :

Analysis :

Here we have to form equations. Then after equating the equations we can find the present ages.

Explanation :

Let the present age of two brothers be 3x years & 4x years.

Now,

Five years ago their ages will be,

• (3x - 5) years
• (4x - 5) years

It is given that five years back their ages were in the ratio of 5 : 7.

☯ According to the question,

⇒ (3x - 5)/(4x - 5) = 5/7

By cross multiplying,

⇒ 7(3x - 5) = 5(4x - 5)

Expanding the brackets,

⇒ 21x - 35 = 20x - 25

Transposing 20x to LHS and -35 to RHS,

⇒ 21x - 20x = -25 + 35

⇒ x = 10

∴ x = 10.

Their ages :

• 3x = 3 × 10 = 30 years
• 4x = 4 × 10 = 40 years

The present age of the two brothers are 30 years and 40 years respectively.