View Full Version : using more than one unknown: 4 oldest ages sum 384 yrs

porgy

10-06-2008, 01:55 PM

The four oldest people in Golden City have lived a total of 384 years put together. The difference in ages for the youngest and the second oldest is 14. The second youngest is 3 years older than the youngest. The oldest is 20 years older than the average of the second oldest and youngest. Find their ages and enter them from youngest to oldest.

Please help! I have no idea what the formula is or where to begin.

tkhunny

10-06-2008, 03:09 PM

no idea what the formula is

There's your problem, right there. What formula? You've been studying agebra so that you can write what you need.

I have no idea ... where to begin.

That's just false. You can define variables. You can manipulate equations. Where's the "no idea" part?

The four oldest people in Golden City have lived a total of 384 years put together. The difference in ages for the youngest and the second oldest is 14. The second youngest is 3 years older than the youngest. The oldest is 20 years older than the average of the second oldest and youngest. Find their ages and enter them from youngest to oldest.

Please help! I have no idea what the formula is or where to begin.

The four oldest people in China. Define their ages.

C1 = Age of Youngest of the four

C2 = Age of Second Youngest

C3 = Age of Second Oldest

C4 = Age of Oldest

That all there is to it. Now translate.

"The four oldest people in Golden City have lived a total of 384 years put together."

C1 + C2 + C3 + C4 = 384 -- You can do that.

"The difference in ages for the youngest and the second oldest is 14."

C3 - C1 = 14 -- You can do that.

Okay, I'm tired. You do the rest, since we've established that you CAN do it.

"The second youngest is 3 years older than the youngest."

{TRANSLATE}

"The oldest is 20 years older than the average of the second oldest and youngest."

{TRANSLATE}

{SOLVE} You will need substitution and the ability to pay attention.

Loren

10-06-2008, 03:33 PM

Name things.

a is age of youngest.

b is age of 2nd youngest.

c is age of 2nd oldest.

d is age of oldest.

Now, use the written statements to determine the expressions that represent the age of each. For instance...

"The difference in ages for the youngest and the second oldest is 14" becomes c-a=14.

You do the same for the other statements.

You are told that a+b+c+d=384. Just plug your derived statements of each person's age into this equation and solve. Before "plugging in" I got each statement in terms of a. For instance, c-a=14 became c=14+a. When I did the "plug in" my main equation was expressed in a's and was easy to solve. As a starting check, I got a=85.

tkhunny

10-06-2008, 04:21 PM

Name things.It's pretty sad when I fail to quote me and it requires someone else to pick up the slack. :wink:

porgy

10-06-2008, 06:16 PM

tkhunny and Loren,

Thanks for the help! I finally got it.

Porgy

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