# Mathematics: How far of a spacing do I need between footings?

A concrete slab is 32 feet long.  I want to cut 2x2 foot squares to install footings, and I need four of them.  What should the spacing be between footings?  Assume that the first footing starts at 0 feet and the last footing ends at 32 feet.
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This is homework.

The footings have centerlines.

The outer centerlines are in one foot from each end of the beam.

Now work it out.
Commented:
Four footings of 2 ft each takes up 2*4 ft, leaving 32-2*4 ft
With 4-1 spaces between the them, that makes (32-2*4)/(4-1)  ft per space

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StatisticianCommented:
This sounds a lot like homework.  Hence I have given clues on how to do it, not the answer.

You have 32 feet along the side of the slab.
You will have four footings each taking up 2 foot , meaning (4 * 2 = ?) feet is occupied by footings.

We assume that you want the space between footings to be equal, so that you have (32 - ?) to be divided up into the interfooting spaces.

So, with four footings you will have  ?? (you can calculate the number)  interfooting spaces between the four footings.

When you divide the remaining available interfooting space by the number of required interspaces you get the common distance from one footing to the next.

The first footing will be at 0 to 2 feet distance from the corner.

The first interfooting space will start at 2 foot from the corner.

Now add on the interfooting spacing and also the footing width, for the next (and next and so forth) footings.

This will give you the start and finishing distances (from the first corner) of the footings.
Author Commented:
How very astute of you Thinkpads User, Ozo and Shanon EE!  Yes, it is homework, but it's not school related!  I have to dig footings to avoid an expired building permit at my house where I want to build a backyard patio cover, but I think I figured it out and cut the cement today - which was as fun as when I learned to ride a bike!  :(

But yes, I drew it on graphing paper and figured out that they need to be 8 feet apart.  Thank you for your input.