Math Is Fun Forum

co32r2r4

Guest

Age problem plz help !!!

The sum of 6 times jacks age and 5 times larrys age is 63. Jack is 1 year less than 3 times as old as larry. find each of their ages. :)

It says to use two equations with two variables to solve!!

co32r2r4

Guest

Re: Age problem plz help !!!

please help, im really having troble with these kind of problems. 

polylog

Member

Registered: 2006-09-28

Posts: 162

Re: Age problem plz help !!!

J := jacks age
L := larrys age

"The sum of 6 times jacks age and 5 times larrys age is 63" means:

6J + 5L = 63

"Jack is 1 year less than 3 times as old as larry" means:

J = 3L - 1

Now just solve these

co32r2r4

Guest

Re: Age problem plz help !!!

How do u solve 6J + 5L = 63 ????

polylog

Member

Registered: 2006-09-28

Posts: 162

Re: Age problem plz help !!!

Well, you are not solving ONLY that equation -- that equation has *2* unknowns, so you cant solve it by itself.
you are solving *both equations simultaneously*,  6J + 5L = 63 AND J = 3L - 1. 

So here is what you do:

We know that  6J + 5L = 63

But we know  also that J = 3L - 1

So substitute this second fact about J into the first equation:

6(3L - 1) + 5L = 63

18L - 6 + 5L = 63

23L = 69 

L = 3

Now you can go back to either equation and get J.

co32r2r4

Guest

Re: Age problem plz help !!!

ty so much u helped me alot. :D:D

polylog

Member

Registered: 2006-09-28

Posts: 162

Re: Age problem plz help !!!

You're welcome.