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The prime factor decompositions of 60 and 2240 are shown below.

60 = 2² x 3 x 5
2240 = 2⁶ x 5 x 7

Which of the following are common multiples of 60 and 2240?
Select all of the correct answers.
a. 2⁴ x 3 x 5² x 7
b. 2⁴ x 3 x 7
c. 2⁶ x 3 x 5 x 7²
d. 2² x 5
e. 2⁸ x 3 x 5² x 7
f. 2² x 3 x 5
g. 2⁶ x 3 x 5 x 7
h. 2⁶ x 5 x 7

User Chao Zhang
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Final answer:

The correct common multiples of 60 and 2240 from the given options are (c) 2⁶ x 3 x 5 x 7² and (g) 2⁶ x 3 x 5 x 7, because they contain all necessary prime factors with the appropriate exponents.

Step-by-step explanation:

The question is about finding common multiples of 60 and 2240 based on their prime factor decompositions. To find a common multiple, the prime factors of both numbers must be included in the product, and the exponents for shared bases should be the highest from either number.

60 = 2² x 3 x 5
2240 = 2⁶ x 5 x 7

The common multiple must have at least the factors:
2⁶ (the higher exponent for the common prime factor 2),
5 (common prime factor),
3 (unique to 60 but necessary for a common multiple),
7 (unique to 2240 but necessary for a common multiple).

Checking the options given:

  • (a) 2⁴ x 3 x 5² x 7 is not a common multiple because it only has 2 raised to the 4th power, and we need at least 2 raised to the 6th power.
  • (b) 2⁴ x 3 x 7 suffers from the same issue as (a); it is missing the proper exponent for 2 and does not include the factor of 5.
  • (c) 2⁶ x 3 x 5 x 7² is a common multiple because it has the necessary factors, with sufficiently high exponents.
  • (d) 2² x 5, (e) 2⁸ x 3 x 5² x 7, (f) 2² x 3 x 5, and (h) 2⁶ x 5 x 7 are not common multiples for various reasons, such as lacking a necessary factor or not having the proper exponents.
  • (g) 2⁶ x 3 x 5 x 7 is a common multiple and contains the exact factors of both numbers with the necessary exponents.

Therefore, the correct options for common multiple of 60 and 2240 are (c) and (g).

User AndrewLeonardi
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