Sunday, March 31, 2013

Five years hence, the age of Jacob will be three times that of his son. Five years ago, Jacob’s age was seven times that of his son. What are their present ages?


Five years hence, the age of Jacob will be three times that of his son. Five years ago, Jacob’s age was seven times that of his son. What are their present ages?
Let        present age of Jacob                     = x year
And      present Age of his son is             = y year
Five years hence,
Age of Jacob will                              = x + 5 year
Age of his son will                                       = y + 5year
Given that the age of Jacob will be three times that of his son
x + 5    =3(y+5)
Add 5 both side we get
x         = 3y + 15 - 5
x          = 3y + 10                    … (1)
 Five years ago,
Age of Jacob will                              = x - 5 year
Age of his son will                                       = y - 5year
 Jacob’s age was seven times that of his son
x – 5    = 7(y -5)
Plug the value of x from equation (1)  we get
3y + 10 – 5     = 7 y – 35
3y + 5             = 7y – 35
3y – 7 y          = - 35 – 5
-4y     =  - 40
y         = - 40 / - 4
y          = 10 year
Plug the value of y in equation first we get
x          = 3* 10 + 10
x          = 40 years
Answer is
Present age of Jacob = 40 years
Present age of his son = 10 years

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