Question

A man is four times as old as his son. In 5 years time he will be 3 times as old as his son. What is the present age of the son in years

Answer 1

Answer:

Man's present age : 40 years old.

Explanation:

Let man's age =  

a

Let son's age =  

b

Since a man is 4 times as old as his son, therefore

a

=  

4

b

In 5 years, he will only be 3 times as old as his son, therefore

a

+

5

=

3

(

b

+

5

)

Apply substitution method :

4

b

+

5

=

3

b

+

15

b

=

10

∴  

a

=

40

Step-by-step explanation:

Answer 2

Answer:

10

Step-by-step explanation:

son's age: x

father's age: 4x

After 5 years:

son's age: x+5

father's age: 3x

so, the age of son is 10:

10×4=40

After 5 years:

15×3=45