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### Order of Operations Problems - a General Strategy

```Date: 10/23/2002 at 17:21:09
From: Kara
Subject: Multiples

My homework was really hard. Can you tell me the answer to this
problem?

Make an equation using 7, 26, 46, and 15 to equal 160.

I have worked it out several different times and still cannot figure
it out. Here's another one: how can you get 18, 9, 24, and 20 to equal
18? At first I thought they looked easy, but I was wrong. Please help
me.
```

```
Date: 10/23/2002 at 18:02:58
From: Doctor Ian
Subject: Re: Multiples

Hi Kara,

For a question like this, the answer is unimportant. The purpose of
the question is to get you to generate a lot of _wrong_ answers, since
that will give you practice in doing arithmetical operations
(addition, subtraction, multiplication, and division). If we told you
the answer, it would be sort of like going to soccer practice in your
place. What would be the point?

In the second part, I can give you this hint: It's possible to use
9, 24, and 20 to make 36; and 36 - 18 = 18.

That, by the way, is a general sort of strategy you can use.  Pick
out one number, and the result, and think about how you could get to
the result in one step using that number. For example, to get to 160
from 15, you might do one of these:

160 = 15 + 145

= 15 * 12

= 175 - 15

= 2400 / 15

So now you have a set of smaller problems:  Can you use the other
three numbers to make 145, 12, 175, or 2400?  If not, you can try
again using one of the other numbers as your choice.

Does this help?

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
Elementary Puzzles
Middle School Puzzles

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