# Simple Algebra Problem

• Jan 13th 2011, 10:38 PM
silvastreak
Simple Algebra Problem
Hi all,

I have a simple algebra problem that has been bugging me :)

"....the product of two numbers is 30. Their average is 6. What are the two number?"

I know this problem is easy; but, I cant seem to work it out.

I pretty much started out like this :

(a) let's say the numbers are X and Y

(b) so, average is 6. Meaning : (x+y) / 2 = 6

(c) Hence, x+y = 12

(d) Product : x * y = 30

(e) So : (x+y=12) and (x*y=30)

(f) Next, I decided to equate both expressions :

10(x+y) = 120

4(x*y) = 120

(g) So : 10(x+y) = 4xy

And, this is where I got stumped
• Jan 13th 2011, 10:44 PM
Unknown008
Equating them wasn't much use since you didn't eliminate any of the numbers...

What you could do is:

x + y = 12

xy = 30

So,

x = 12 - y

Substitute in the other equation;

y(12 - y) = 30

Can you finish it? :)
• Jan 13th 2011, 10:50 PM
silvastreak
Now, I feel SOOOOOOOOOOO stupid :) :)

Thanks )))
• Jan 13th 2011, 10:52 PM
Unknown008
You're welcome (Smile)