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chapter1.7b
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à 1.7èWhole Numbers in Prime Factored Form.
äïPlease write the following Whole Numbers in Prime
êêFactored Form.
âS
êêêï1)ï6è=è2 ∙ 3
êêêï2)ï18è=è2 ∙ 3 ∙ 3
éS
To write the Whole Number 6 in Prime Factored Form, you
should break it down into products of prime numbers.ïThe prime numbers
are described in the following list.
êêï2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ...
Each of ç numbers has the property that the only factors they have
are "1" and the number itself.ïThe Whole Number, 6, is not a prime
number.ïIt is a "composite" number, and composite numbers can be
factored into products of prime numbers.ïSince "6" factors into the
product of the two prime numbers, 2 and 3, the Prime Factorization of
6 is 2 ∙ 3.èThus, 6è=è2 ∙ 3.
To express the Whole Number "18" in Prime Factored Form, you should
start with the smallest prime number, 2, and see if it divides evenly
into "18".ïSince 2 goes into 18 nine times, you can express 18 as 2∙9.
Also, since the next smallest prime number, 3, divides evenly into 9,
18 can be expressed as 2 ∙ 3 ∙ 3.ïSince ç factors are all prime
numbers, the Prime Factorization of 18 is 2 ∙ 3 ∙ 3.
êêêïThus,ï18è=è2 ∙ 3 ∙ 3
1
êêëExpress 12 in Prime Factored Form.
ë A)ï2∙3∙3êïB)ï2∙2∙3êïC)ï4∙3êè D)ïå
ü
êêêê12è=è2∙2∙3
Ç B
2
êêëExpress 24 in Prime Factored Form.
ë A)ï8∙3êè B)ï4∙6êè C)ï2∙2∙2∙3êD)ïå
ü
êêêê24è=è2∙2∙2∙3
Ç C
3
êêëExpress 19 in Prime Factored Form.
ë A)ïprimeêïB)ï18∙1êèC)ï10∙9êèD)ïå
ü
êêêê19 is prime
Ç A
4
êêëExpress 75 in Prime Factored Form.
ë A)ï25∙3êèB)ï3∙5∙5êïC)ï5∙7∙5êïD)ïå
ü
êêêê75è=è3∙5∙5
Ç B
5
êêëExpress 90 in Prime Factored Form.
ë A)ï2∙3∙3∙5êB)ï2∙5∙9êïC)ï2∙45êèD)ïå
ü
êêêê90è=è2∙3∙3∙5
Ç A
6
êêëExpress 105 in Prime Factored Form.
ë A)ï3∙5∙7êïB)ï21∙5êèC)ï3∙35êèD)ïå
ü
êêêë 105è=è3∙5∙7
Ç A
7
êêëExpress 206 in Prime Factored Form.
ë A)ï2∙3∙10ê B)ï2∙103êïC)ï2∙2∙3∙3∙7ëD)ïå
üêêê206è=è2∙103
è Note the difficulty in telling whether "103" is a prime number.
In order to see if "103" is a prime number, you should try to divide it
by 2, 3, 5, 7, and 11.ïSince none of ç prime numbers divide evenly
into 103, you know that "103" is itself prime.ïIt is not necessary
to see if "13" will divide evenly into 103 because 13∙13 = 169 is
larger than 103.
Ç B
8
êêëExpress 125 in Prime Factored Form.
ë A)ï3∙5∙5êB)ï3∙3∙5∙5êC)ï5∙5∙5êïD)ïå
ü
êêêë 125è=è5∙5∙5
Ç C
9
êêëExpress 67 in Prime Factored Form.
ë A)ï9∙7êè B)ïprimeêïC)ï3∙3∙7êïD)ïå
ü
êêêë 67 is prime.
Ç B
10
êêëExpress 78 in Prime Factored Form.
ë A)ï2∙3∙13ë B)ï2∙7∙7êïC)ï2∙3∙11ê D)ïå
ü
êêêê78è=è2∙3∙13
Ç A
11
êêëExpress 144 in Prime Factored Form.
ë A)ï8∙2∙3êïB)ï9∙16êèC)ï2∙2∙2∙2∙3∙3èD)ïå
ü
êêêë144è=è2∙2∙2∙2∙3∙3
Ç C
12
êêëExpress 180 in Prime Factored Form.
ë A)ï2∙2∙3∙3∙5ëB)ï4∙5∙9êïC)ï2∙2∙5∙9êD)ïå
ü
êêêë180è=è2∙2∙3∙3∙5
Ç A