# I'm not understanding this problem

• Dec 11th 2006, 01:07 PM
Angel King
I'm not understanding this problem
• Dec 11th 2006, 01:11 PM
topsquark
Quote:

Originally Posted by Angel King

39 squared = 39^2 = 39 * 39 = 1521

-Dan
• Dec 11th 2006, 09:02 PM
CaptainBlack
Quote:

Originally Posted by Angel King

I think we would be interested in why you find this a problem?

Is it that you don't know what 39 squared means? ( it means 39 times itself
which is 39x39).

Or that you cant do the multiplication?

RonL
• Feb 1st 2007, 05:58 AM
AlvinCY
There are many other ways to attack the problem, the box method which is long and tedious, simple multiplication, calculator... otherwise if you know the perfect square expansion:

39^2 = (40 - 1)^2... mainly cos 40 and 1 and nice numbers to work with.
= (40)^2 - 2*(40)*(-1) + 1^2
= 1600 + 80 + 1
= 1681
• Feb 1st 2007, 08:51 AM
CaptainBlack
Quote:

Originally Posted by AlvinCY
There are many other ways to attack the problem, the box method which is long and tedious, simple multiplication, calculator... otherwise if you know the perfect square expansion:

39^2 = (40 - 1)^2... mainly cos 40 and 1 and nice numbers to work with.
= (40)^2 - 2*(40)*(-1) + 1^2
= 1600 + 80 + 1
= 1681

Except we do hope to get the right answer

RonL
• Feb 1st 2007, 02:47 PM
AlvinCY
Sorry. Change of signs... it was nearly 3 am wen I posted it, what I meant was in fact:

$\displaystyle 39^2$
$\displaystyle = (40 - 1)^2$
$\displaystyle = 40^2 - 2 \times 40 \times 1 + 1^2$
$\displaystyle = 1600 - 80 + 1$
$\displaystyle = 1521$