The present age of Harini's father is 4 times the present age of Harini. And the age difference of Harini's father and mother is 5 years. Five years ago, the sum of all the three person's age was 70 years. Which of the following could be the present age of Harini's father?
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Let F be the father's age, M be the mother's age and H be Harini's age. Then we have
F = 4 H ⟹ H = 4 F ( 1 )
F − M = 5 ⟹ M = F − 5 ( 2 )
F − 5 + M − 5 + H − 5 = 7 0 ⟹ F + M + H = 8 5 ( 3 )
Substitute ( 1 ) and ( 2 ) in ( 3 ) . We have
F + F − 5 + 4 F = 8 5
2 . 2 5 F = 9 0
F = 4 0
suppose,Harini's age=x, her father's age=y=4x, her mother's age=z. now,y-z=5......(1) as the sum of their age was 70 before 5years,now it will be 85.. so,now,we get, x+y+z=85 =>y/4+y+y-5=85 =>y=40 so,her father's present age is40
for present ages => Harini = x .....her father = 4x......her mother = 4x -5 their age 5 years back harini= x -5 ....... her father = 4x-5 ...... her mother = 4x -10... now we get the eq . (x-5)+(4x-5)+(4x-10) = 70 = 10 .........father's age =4x =40
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Father is 4 times Harini so F=4h.
Father and mother age difference is 5 so
Abs(f-m)=5 so f-m=5 or m-f=5.
3 years ago sum was 70 so
F-3+m-3+h-3=70.
Simplify to f+m+h-15=70 so F+m+h=85 => F+m+f/4=85.
Case 1: mother is older means that.
F+(f+5) +f/4=85 => 9f/4=80 => F=35.5555... Not an integer makes no sense.
Case 2: father is older means that
F+(f-5)+f/4=85 => 9f/4=90 => F=40 which is an integer so the father must be older. Therefore the father is 40 years old.