Math Is Fun Forum

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: Finding the area using Pythagoras

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

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob