age related question

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• Dec 11th 2011, 07:05 AM
haftakhan
age related question
Is this question right or some information is missing in it ?

In 5 years time father will be 3 times as old as his son. four years ago father was 6 times as old as his son.

Find their present age ?

Can anyone help me solve it if its correct
• Dec 11th 2011, 07:25 AM
skeeter
Re: age related question
Quote:

Originally Posted by haftakhan
Is this question right or some information is missing in it ?

In 5 years time father will be 3 times as old as his son. four years ago father was 6 times as old as his son.

Find their present age ?

Can anyone help me solve it if its correct

let f = father's present age

s = son's present age

Quote:

In 5 years time father will be 3 times as old as his son
f + 5 = 3(s + 5)

Quote:

four years ago father was 6 times as old as his son
f - 4 = 6(s - 4)

yes, the system of equations has a unique solution.
• Dec 11th 2011, 07:26 AM
e^(i*pi)
Re: age related question
Quote:

Originally Posted by haftakhan
Is this question right or some information is missing in it ?

In 5 years time father will be 3 times as old as his son. four years ago father was 6 times as old as his son.

Find their present age ?

Can anyone help me solve it if its correct

With these problems it's always good to write down what you know using variables. Let the father's age now be \$\displaystyle x\$ and the son's age now be \$\displaystyle y\$.
Now we can write a number of equations based on what we're told:

In 5 years time father will be 3 times as old as his son: \$\displaystyle x+5 = 3(y+5)\$

four years ago father was 6 times as old as his son: \$\displaystyle x-4 = 6(y-4)\$

You now have a pair of simultaneous equations in x and y so you can solve it. In this case it would be easier to use elimination by taking the second equation from the first