Posted by **TUHITUHI** on Saturday, October 6, 2012 at 12:19pm.

Sanjeev is twice as old as his son.If after four years he will be four times as old as his son was 9 years ago ,how old is each now ??

- math -
**Anonymous**, Saturday, October 6, 2012 at 2:27pm
Let's let J represent Sanjeev and x represent his son.

If J is twice as old as S then the equation is 2x=J

After four years, so J+4, he is four times as old as his son, so 4x, was 9 years ago, so x-9, if you combine all the parts of that statement you get the equation: 4(x-9)= J+4.

So now you have two different equations:

2x=J

4(x-9)=J+4

So now you just substitute. We know that J=2x from the first equation so substitute 2x in for J in the second equation and solve for x:

4(x-9)=(2x)+4

4x-36=2x+4

2x-36=4

2x=40

x=20

so now we know that the son is 20 years old. Then plug in 20 for x in the first equation to find Sanjeev's age:

2(20)=J

40=J

So Sanjeev is 40

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