Question

A man's age is 4 times his son's age after 5 years he will be 3 times as old as his son.
Find their present ages . ​

Answer 1

Answer:

The present ages of son and father are 10 years and 40 years respectively.

Step-by-step explanation:

Given :

Man's age = 4 times the age of his son

After 5 years man will be = thrice the age of his son

To find :

Their present ages

Solution :

Let the present ages be -

• Son as y
• Father as 4y

$\rule{300}{1.5}$

Ages after 5 years -

• Son = (y + 5)
• Father = (4y + 5)

$\rule{300}{1.5}$

⇒ 4y + 5 = 3(y + 5)

⇒ 4y + 5 = 3y + 15

⇒ 4y - 3y = 15 - 5

⇒ y = 10

Son's present age = 10 years

$\rule{300}{1.5}$

★ Value of 4y

⇒ 4(10)

⇒ 40

Father's present age = 40 years

$\therefore$ The present ages of son and father are 10 years and 40 years respectively.

Answer 2

Step-by-step explanation:

Man's present age : 40 years old.

Let man's age = a

Let son's age = b

Since a man is 4 times as old as his son, thereforea = 4b In 5 years,

he will only be 3 times as old as his son, thereforea+5=3(b+5)

Apply substitution method :

4b+5=3b+15 b=10

∴ a=40