8 dimes, 5 quarters, 4 half dollars

Date: 13 Jan 1995 10:59:48 -0500
From: Anonymous
(Mellisa, Laura and Jacob)
Subject: Money Problem

From: Mellisa, Laura and Jacob
Dear Dr. Math, Please help us answer this problem:

Jacob has 8 dimes, Laura has 5 quarters and Mellisa has 4 half dollars. 
How much is it all together?

Thank you for your help.

Date: 13 Jan 1995 12:08:39 -0500
From: Dr. Ken
Subject: Re: Money Problem

Hello there!

This is a really neat problem.  The key to solving it is to just take a
little part of the problem at a time, and pretty soon you'll have solved the
whole thing!

Here's what we'll do: we'll figure out how much money each person has, 
and then we'll add those three figures together.

So first let's figure out how much Jacob has.  You said he has 8 dimes, and
each dime is worth 10 cents.  So you can either write it out like this:
10 + 10 + 10 + 10 + 10 + 10 + 10 + 10    or like this:
10 x 8.

They mean the same thing; it's just a question of whether you want to do a
long addition problem or a short multiplication problem.

So either way, I think we get 80 cents for Jacob.  Do you see how that
works?  Let's remember how much Jacob has and come back to it later.

So let's figure out how much money Laura has!  If she has 5 quarters, and
each quarter is worth 25 cents, how much money does she have?  we can 
either do it with addition (25 + 25 + 25 + 25 + 25) or with multiplication 
(25 x 5). Since these numbers are a little trickier, I'll help you with it.  
We get either 

   2                          2
   25                         25
 + 25            or         x  5
 + 25                       ----
 + 25                        125
 + 25
 ----
  125

Does that make sense to you?  There's a two on top of each one of the
computations, and they're twos that I "carried."

So it looks like Laura has 125 cents (which is also known as $1.25).

Finally, let's figure out who much money Mellisa has!  If she has 4 half
dollars, and each half dollar is worth 50 cents, how much does she have?
Well, you either do it by adding 50 + 50 + 50 + 50 or multiplying 50 x 4.
I think I'll let you do this one by yourselves.  When I do it, I get 200
cents (also known as $2.00).

So now we can add up the money that everybody had.  We'll set it up as 
an addition problem:

    80
 + 125
 + 200
------
   ???


Do you think you can handle adding these together by yourself?  You'll 
have to do a little carrying, but not much.  I hope you enjoyed this!

-Ken "Dr." Math