All spiders are things with eight legs. All black widows are spiders, therefore all black widows are things having eight legs. I need help shading the venn diagram.

Draw a circle, label it "All spiders". Draw a 2nd circle COMPLETELY INSIDE it (like a target). Label the 2nd circle "Black Widows". This shows that All black widows are spiders and therefor have 8 legs.

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Originally Posted by andlie

All spiders are things with eight legs. All black widows are spiders, therefore all black widows are things having eight legs. I need help shading the venn diagram.

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Hello andlie,

Actually you will need three circles overlapping. You have probably noticed that you have three different terms, i.e. spiders, Black Widow and eight legs. Each occurs twice.

Spider is the middle term and as such it appears twice, therefore it will not appear in the conclusion. There must be a major term in the syllogism and it will appear as the predicate of the conclusion.

This is why it is a good idea to label your syllogism M for the middle term, S for the minor term and P for the major term. It is also a good idea to label your circles with these terms.

You should come up with something like this before you draw your circles.

All spiders are eight legged
(All M are P)

All Black Widows are spiders
( All S are M

T/F All Black Widows are eight legged
(All S are P)

What you should notice when you do the shading is that the only unshaded area of S is in all three classes. It is also important to note that the area S is completely within the P class.

Good luck with it.