The work that Yi did to find the greatest common factor of 42 and 63 is as follows Factors of 42: 1, 2, 3, 6, 7, 14, 21, 42 Factors of 63: 1, 7, 9, 63 The greatest common factor is 7. What is Yi’s error?
Answer
A
Yi found the least common multiple.
B
Yi did not list all the factors of 63.
C
Yi did not list all the factors of 42.
D
Yi listed multiples for each number instead of factors.
Explanation
Yi did not list all the factors of 63. The factors include 1, 3, 7, 9, 21, and 63, so Yi left out 3 and 21. Since 21 is also a factor of 42, the greatest common factor is 21, not 7.
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