OG 11math-PS-Q209

leadinglifesl · 发表于 2006-11-25 14:45:00

How many different positive integers are factors of 441?

choices are: 4,6,7,9,11

answer is 9.

Can anyone tell me why?Thanks.

raj_sharma · 发表于 2006-11-25 23:32:00

441
=3*147
=3^2*49
=3^2*7^2
total numbers of factors will be :
(2+1)*(2+1)

leadinglifesl · 发表于 2006-11-26 01:16:00

raj_sharma,

Thank you.But what I think is because 441=3*3*7*7 or 1*441,this means there are 4 different factors.Why am I wrong? Is your (2+1)*(2+1) a general formula for any questions like this?Pls help.Thanks again.

songren · 发表于 2006-12-16 22:57:00

3.9.21.7.49.63.147.441.1

OG 11math-PS-Q209

OG 11math-PS-Q209

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