Ans:

solve for x and y...I tried solving by elimination and substitution by taking LCM etc but the answer I obtain doesn't match with the answer key.

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- Jul 13th 2008, 08:08 AMice_syncerTricky linear equations in two variables question

Ans:

solve for x and y...I tried solving by elimination and substitution by taking LCM etc but the answer I obtain doesn't match with the answer key.

- Jul 13th 2008, 08:14 AMtopsquark
I'm a bit confused. It looks like you want a solution to the system of two equations for x and y in terms of a and b. But if you plug in your given answer you get two equations in a and b which you can solve for a and b. Are the and conditions extra equations to put into the system? You can do this (I haven't tried yet) ,but you will not get your given solution.

-Dan - Jul 13th 2008, 10:36 AMice_syncer
- Jul 13th 2008, 10:40 AMice_syncer
- Jul 13th 2008, 10:52 AMIsomorphism
- Jul 14th 2008, 04:26 AMice_syncer
Too late, I got the answer by the same method some 5 hours ago....

What about the below question ? Are you getting 15?

Father’s age is three times the sum of ages of his two children. After 5 years his age will be twice the sum of age of his two children. Find the age of father. - Jul 14th 2008, 05:00 AMIsomorphism
Well you can check it on your own instead of asking other people. So do a little backtracking...

**Backtracking:**

IF fathers age is really 15 then the sum of ages of children must be 5. 5 years from now, his age will be 20 and both the children's age will advance by 5. Thus totally the sum of their ages will be 15 after 5 years. BUT two times 15 is not 20!

So your answer is wrong.

Let the fathers age be '3x', then the sum of children's age is x. 5 years from now fathers age will be 3x+5, but the sum of children's age will be x+10. Remember that there are two people and both of them advance by 5 years.**Working out:**

Now by given data:

So fathers age is 3x =**45 years.**

Now backtrack this and see if its right!