The present age?

Algebra Level 1

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?

50 years 48 years 44 years 40 years

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4 solutions

Lisa O
Jul 2, 2015

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.

Let F F be the father's age, M M be the mother's age and H H be Harini's age. Then we have

F = 4 H F=4H \implies H = F 4 H=\dfrac{F}{4} ( 1 ) \color{#D61F06}(1)

F M = 5 F-M=5 \implies M = F 5 M=F-5 ( 2 ) \color{#D61F06}(2)

F 5 + M 5 + H 5 = 70 F-5+M-5+H-5=70 \implies F + M + H = 85 F+M+H=85 ( 3 ) \color{#D61F06}(3)

Substitute ( 1 ) \color{#D61F06}(1) and ( 2 ) \color{#D61F06}(2) in ( 3 ) \color{#D61F06}(3) . We have

F + F 5 + F 4 = 85 F+F-5+\dfrac{F}{4}=85

2.25 F = 90 2.25F=90

F = 40 F=40

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

Tootie Frootie
Jul 1, 2015

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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