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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,465

hi

I kept this problem on 'subscription', as I was hopeful of coming up with a grade 9 solution using Pythagoras.

Here it is.

Set up a spreadsheet with 'w' as a variable.

use formulas to compute

y = root(30*30 - w*w)

x = root(40*40-y*y)

z = root(50*50-x*x)

Compute w + x - y - z. For a square this value should be zero.

Use goal seek to 'find' a value of zero by varying w.

The screen shot from Excel shows the formula set up and the goal seek command with the finished values.

I have used goal seek with this age of child so I think it is a valid method.

Sorry it has taken so long to dream it up.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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