Please take a look at the two sentences below which I quoted from http://www.cacr.caltech.edu/~sean/projects/stlib/html/numerical/numerical_random_poisson.htm.

"I have adapted some methods from various random number packages. Each of them are hybrid methods."

Isn't the second sentence gramatically wrong for using 'are'? If it is not, please explain.

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Comments  (Page 2) 
Mister MicawberMathematicians are not the best writers
I see that the question has been more than adequately answered. I can't contribute anything more than a smiley after the comment about mathematicians and English.

And why are you laughing?Emotion: rofl

Sorry. You're incorrect.

EACH equals ONE.......as in "each one".

e.g. You never see/hear "each two" or "each three".

Even though the word ONE is not always or even USUALLY spoken or written in accompaniment with EACH, it is ALWAYS implied/understood.

"Each (one) of these children is attending school."

"Each of my cats has (NOT have) particular likes and dislikes when it comes to food."

"Each of you is (NOT are) responsible for your own transportation."

Students: We have free audio pronunciation exercises.

As an American EFL teacher, I would say that it has to be "is," but a popular (British) text, face2face, says both forms are acceptable ( reference material, p. 137 of the upper intermediate book), though in the chapter on neither, both, any etc., only the plural form is sued.