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### How Old at \$4,000?

```Date: 10/15/2002 at 17:48:57
From: Stephen
Subject: Word Problem

Aunt Isabella sends money to each niece and nephew on his or her
birthday. She gives each child \$10.00 on his or her first birthday.On
each birthday thereafter, you and your cousins get \$20.00 more than
on the birthday before. How old will you be when you receive a total
of \$4,000.00 from Aunt Isabella?
```

```
Date: 10/15/2002 at 20:12:33
From: Doctor Ian
Subject: Re: Word Problem

Hi Stephen,

gives you 1 of them on your first birthday, 3 the next one, 5 the next
one, and so on.

Suppose you save them, and use a magic marker to mark each one with
the number of the birthday when you got it. Then you lay them out on a
table like this:

[1] [2] [3] [4]

[2] [2] [3] [4]

[3] [3] [3] [4]

[4] [4] [4] [4]

Do you see how each birthday adds one more 'layer' to the square?

How big would the square have to get for you to have 400 ten-dollar
bills (which is the same as \$4000)? How many years would it take to
get that big?

- Doctor Ian, The Math Forum
http://mathforum.org/dr.math/
```
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