# How is this a truth table?

I do not understand how this is a truth table and not a Kmap. I’m very confused as to how to get the answer. To me this looks like a Kmap. Can someone explain the problem? Thanks

Hey thanks for your post! Because this is an assessment question, we can’t exactly give too much help with this one. However, I recommend checking out the lecture recording for Boolean Algebra here (start watching at 13:20).

Hint - you may need to do some re-ordering!

I think it’s just a simplified version of a whole/complete truth table, which would have way more cells.

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Its a tricky question for sure! remember how Kmaps are supposed to be setup as opposed to truth tables

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Kmaps take a truth table and help it make it easier to find patterns so you can extract a simplified Boolean Function which is great when working with binary (especially digital circuits). In other words, the way I look at it is, Kmaps are simplified truth tables.

And if it helps you, that table is all you need to find the simplified expression. If you look something up in the book or online and it says to get the simplified expression you need to identify groups of 1s from your Kmap, then you can use what is given in your screen shot to start find those groups of 1s. Good luck!

@Staff-Katherine
I laughed at the Hint. I triple-checked this assessment before turning it in and got it first go, but this would have been the question that brought me down if I hadn’t tripled checked. That reordering is super subtle if you’re not paying attention.

Because this video is no longer available, can someone provide some help here? I’m stuck on this one.

I thought truth tables have an ‘output’ column, where this does not yet it’s called a truth table. Quoting the pre-assessment material “A Boolean operator can be completely described using a table that lists the inputs, all possible values for the inputs, and the resulting values of the operation for all possible combinations of these inputs. A table like this is called a truth table .”

Hi Mark,
Truth tables and K-maps can look very similar. However, with K-maps, there are very specific rules about how the rows and columns are set up, and this is what allows us to find patterns and use them to simplify an expression.

Go back and review the content for K-maps - and look for an answer to the question below:

• How must the values in the header row and header column be organized in a K-map?

I think you’ll notice it once you find that detail in the lesson.
Jesse

Hi Mark,
Thank you for pointing out that the video is no longer available. We were able to find the same video at another link. You can access the recording here.