Question

5 years ago father's age was 7 times the age of his son 5years later the father age will be 3times of the age of his son find their present age
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Answer 1

Answer:

father's present age is 40

son's present age is 10

Step-by-step explanation:

let present age of son be x

let present age of father be y

5 years ago son was x - 5 years old

5 years ago father was y - 5 years old

but 5 years ago father's age was 7 times the age of his son

so 7 ( x - 5 ) = y - 5

=> 7x - 35 = y - 5

=> 7x - y = - 5 + 35

=> 7x - y = 30  

=> y = 7x - 30   -------------------------------- >   EQUATION 1

5 years later son will be x + 5 years old

5 years old father will be y + 5 years old

but 5 years later the father's age will be 3 times of the age of his son

=>  3 ( x + 5 ) = y + 5

=> 3x + 15 = y + 5

=> 3x - y = 5 - 15

=> 3x - y = - 10

=> y = 3x + 10    -------------------------------- >   EQUATION 2

from equations 1 and 2:

y = 7x - 30 and y = 3x + 10

=> 7x - 30 = 3x + 10 ( LHS and LHS are equal in equation 1 and equation 2 since y = y , so RHS and RHS will be equal )

=> 7x - 3x = 10 + 30

=> 4x = 40

=> x = 40 / 4

so x = 10

applying x = 10 in equation 1 :

y = 7x - 30

= 7 ( 10 ) - 30

= 70 - 30

= 40

x = 40

y = 10

therefore son's present age is 10 and father's present age is 40