Multiplying by a Decimal

Date: Thu, 10 Nov 1994 19:37:12 CST
From: Anonymous

Dr. Math,

I am in the 4th grade and I would like to know the answer to this 
question. How come when you multiply 0.36 and 88 you get 9.4270,
which is less than what it should be?

I like math very much and I am glad you can help me when I have 
questions.

Thanks, Richard

Date: Thu, 10 Nov 1994 20:54:28 -0500 (EST)
From: Dr. Ken
Subject: Re: your mail

Well Richard,

I am very impressed that you noticed that 9.427 is smaller than
the answer should be.  You are right.  That is too small.  The reason 
it seems too small is because it is not the right answer.

I would encourage you to try again to see if you can get an
answer that makes more sense to you.  If you still can't get it write 
back and we will give you some more help.

-Ken "Dr." Math

Date: Thu, 10 Nov 1994 20:25:05 CST
From: Anonymous
Subject: Re: your mail

Dear Dr.Math,

    I am  Richard Griffin's brother, William Griffin. I am in 6th grade. I 
had the answer explained to me by my dad. He's a banker.  He said that 
when you multiply something like 0.5 and 4 it is less than four because 
it is sort of like taking 0 and 4, but instead of taking it all the way to 
0 it takes a percentage of it like 50% and so it makes the answer 50% less than
4, which is 2. Please correct me if I am wrong because my dad isn't the best 
teacher. 

William Griffin

Date: Thu, 10 Nov 1994 22:58:07 -0500
From: Anonymous
Subject: Re: your mail

Richard and William, I'd say your Dad is right.

When you multiply something by 1 what do you get?

3 * 1 = ?

26 * 1 = ?

You just get whatever you started with, right?

And if you multiply by a number greater than 1, then you get an answer
bigger than you started with, right?

3*2=?

26*2=?

So if you multiply by something less than one you will get an answer
smaller than what you started with.

If you multiply by one half then you get half of what you started with.
There are lots of ways to write one half.

1/2 or .5 are two ways.

.5 * 8 = 4

.75 * 8 = 6

Write back if this is not yet helpful enough.

-- Steve