What is -3/10 as a decimal?

So lets first operate with positive numbers. We should go about this by thinking about a pie, like this:

Courtesy of: https://tutor.hix.ai (ClipArt ETC Free Classroom License)

Lets say that the circle above is an apple pie. The apple pie has 10 slices, or parts. If no one takes a piece of the pie then we have all 10 slices of the pie. Since we have all ten slices of pie we can say that we have "10 of the 10 slices" or #10/10#.

#10/10# is a whole, in other words, it is equal to 1, and the equation looks like this:

#10/10= 1#

...or a full pie (this is sweet potato pie):

Courtesy of: https://tutor.hix.ai (Public Domain)

Or this (key lime):

My own photo (and baking), feel free to reuse, if you want the recipe shoot me a message

Okay, now lets say that 9 people enter the room and they all take a slice of the pie. That means there is only on piece of pie left #(10-9= 1)#. This means that we have #1/10# of a pie, since 9 slices were taken. Now #1/10# happens to be the same as #0.1#, as an equation it looks like this:

#1/10= 0.1#

We know this because #10/10= 1# and if we add 0.1 ten times we get 1, like this:

#0.1+0.1+0.1+0.1+0.1+0.1+0.1+0.1+0.1+0.1= 1#

There's an underlying tend here, which looks like this:

#1/10= 0.1#

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#2/10= 0.2#

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#3/10= 0.3#

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#4/10= 0.4#

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#5/10= 0.5#

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#6/10= 0.6#

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#7/10= 0.7#

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#8/10= 0.8#

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#9/10= 0.9#

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#10/10= 1#

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This exact same trend exists for negative fractions we just have to put a negative sign in front of the decimal. This means that:

#-3/10= -0.3#

I hoped this helped!