The product of all the prime numbers less than 20 is closest to which of the following powers of 10 ?
A) 10^9
B) 10^8
C) 10^7
D) 10^6
E) 10^5
OA: C
Source: OG
[spoiler]OG's explanation: The prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17, and 19. Th eir product is 9,699,690 (arrived at as follows: 2*3*5*7*11*13*17*19 = 9,699,690). This is closest to 10,000,000 = 10^7[/spoiler]
Does anyone have a practical and usable method? Thanks in advance.
A) 10^9
B) 10^8
C) 10^7
D) 10^6
E) 10^5
OA: C
Source: OG
[spoiler]OG's explanation: The prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17, and 19. Th eir product is 9,699,690 (arrived at as follows: 2*3*5*7*11*13*17*19 = 9,699,690). This is closest to 10,000,000 = 10^7[/spoiler]
Does anyone have a practical and usable method? Thanks in advance.
