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Multiplying Numbers with Decimals


Date: 12/7/95 at 19:34:41
From: Anonymous
Subject: decimals

What is 9.4 x 9.6?


Date: 12/23/95 at 22:49:2
From: Doctor Elise
Subject: Re: decimals

Hi!  

Okay, this is the way you multiply decimals without a 
calculator:

Basically, it's the same as multiplying whole numbers, 
with a twist!

If you had 94 x 96, you'd do it like this:

   94
 x 96
  ____
  564  (this is 6 times 94) 
 8460  (this is 9 times 94 times 10)
______
 9024  (564 + 8460, which is the answer)

Now, if we have decimals, we count how many 
numbers there are to the right of the decimal
point, like this:

in 9.4, the 4 is to the right of the decimal point
so that's one, and in 9.6 the 6 is to the right
of the decimal point, so that's another, for a total
of 2.

Then we put the decimal point in the answer 2 places
to the left of the 'ones' column, like this:
90.24.  

If you think about it, you know that 9x9 = 81, and
10x10 = 100, so 9.4 x 9.6 has to be between 81 and 100!

Does this help?

-Doctor Elise,  The Geometry Forum

    
Associated Topics:
Elementary Fractions

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