Question

A is three times as old as his son. In ten years, the product of their ages will be 800.How old are they now ?

Answer 1

Solution :
         Let the Present Age of A's son be x years .
       therefore , Present age of A = 3x years

After 10 years,
     A's son's age = x+10
   and A's age = 3x +10

According to Question ,
           ( x+10 )*(3x+10)=800
            x(3x+10)+10(3x+10 )= 800
         3x² + 10x + 30x +100 = 800
         3x² + 40x +100 = 800
         3x² + 40x + 100 - 800 = 0
         3x² + 40x - 700 = 0
By Hit and Trial method ,
         x=10 .
Present age of A's Son = x= 10 years .
Therefore Present age of A = 3x = 3*10 = 30 years

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Answer 2

Let the Present Age of A's son be x years .
So the present age of A = 3x years .

Now A.T.Q

1.After 10 years,
A's son's age = x+10
and A's age = 3x +10

2.
   ( x+10 )(3x+10)=800
    3x² + 10x + 30x +100 = 800
    3x² + 40x +100 = 800
    3x² + 40x - 700 = 0

Solve it with any method you know .
x=10 .

Present age of A's Son = x= 10 years .
Therefore Present age of A = 3x = 3*10 = 30 years