Answer: the present age of son is 15 years, and the present age of father is 45 years.
Step-by-step explanation:
Let the age of son be 'x' and that of his father be 'y'.
So according to the question, the 1st equation that can be formed will be:
y = 3(x) ->(1)
[as father's age is 3 times the age of son]
Now after 5 years:
Age of son = (x+5)
Age of father = (y+5)
So according to the question, the 2nd equation that can be formed will be:
(y+5) = 2.5×(x+5) ->(2)
[as father is now two and half times old as his son]
Substituting the value of equation (1) in (2), we get:
(3x+5) = 2.5×(x+5)
=> 3x + 5 = 2.5x + 12.5
=> 3x - 2.5x = 12.5 - 5
=> 0.5x = 7.5
=> x = 7.5/0.5 = 15
Thus, the present age of son is 15 years.
Note : we can calculate the age of father by putting the value of x in equation (1) or (2):
y = 3(x) = 3 × 15 = 45 (putting x in equation 1)
Thus, the present age of father is 45 years.