Question

will be 9 : 7. Find their present ages.
21. Five years ago a man was seven times as old as his son. Five years hence, the father will be
three times as old as his son, Find their present ages.
After 12 years Manoj will be 3 times as old as he was 4 years ago. Find his present age.​

Answer 1

Answer:

i)40 yrs., 10yrs.

ii)12 yrs.

Explanation:

i) Let the present ages of man and his son be x and y respectively.

ATQ.

Equation 1: x-5 =7 (y-5)

=>x-5=7y-35

=>x-7y= -30

=>7y-x=30

Equation 2: x+5 =3 (y+5)

=>x+5= 3y+15

=>x-3y=10

Adding Eqn. i and ii :

-x +7y = 30

x -3y = 10

+ __________

4y = 40

:. y= 40/4 = 10

Putting y in Eqn.(ii)

x-3×10=10

=> x-30=10

=> x=30+10=40

Thus age of father= 40 yrs.

". ". ". son= 10 yrs.

ii)Let the present age of Manoj be x

ATQ.

x+12=3×(x-4)

=> x+12=3x-12

=> 2x=24

:. x= 12

Thus Manoj is 12 yrs. old..