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B
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D
E
BTGmoderatorDC wrote: ↑Sat Apr 10, 2021 10:09 pmWhich of the following are/is prime?
I. 143
II. 147
III. 149
(A) II only
(B) III only
(C) I & II
(D) I & III
(E) I, II, & III
Solution:
143 is not prime since 143 = 11 x 13, and 147 is not prime since 147 = 7 x 21. However, 149 is prime since its only factors are 1 and 149.
Alternate Solution:
We should immediately realize that 147 is not prime since it is divisible by 3 (which we can tell from the fact that the sum of the digits of 147 is divisible by 3). Thus, we eliminate answer choices A, C and E. To decide between B and D, we only need to determine whether 143 is prime. Since 143 = 11 x 13, it is not prime, and answer choice D is also eliminated. The only remaining answer choice is B.
Answer: B
OA B
Source: Magoosh
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