请教一道数学题

cyx1106 · 发表于 2011-10-1 19:55:23

the product of all the prime numbers less than 20 is closest to which of the follwing powers of 10?
A.10^9
B.10^8
C.10^7
D.10^6
E.10^5

你家兜爷 · 发表于 2011-10-1 20:59:28

选C？

cyx1106 · 发表于 2011-10-1 21:28:10

对的！你一定没有用计算器~请教

cyx1106 · 发表于 2011-10-1 21:28:58

选C？

-- by 会员你家兜爷 (2011/10/1 20:59:28)

对的！你一定没有用计算器~请教

jingnnee · 发表于 2011-10-1 22:04:43

我觉得可以这么想：原题：OG 12 P52-15

选C： 2.3.5.7.11.13.17.19---2*5=10 3*7~20 11~10 13~15 17~15 19~20
10*20*10*225*20~10*20*10*200*20=8*10^6~10^7

the product of all the prime numbers less than 20 is closest to which of the follwing powers of 10?
A.10^9
B.10^8
C.10^7
D.10^6
E.10^5

-- by 会员 cyx1106 (2011/10/1 19:55:23)

cyx1106 · 发表于 2011-10-1 23:45:20

谢谢！~~

cyx1106 · 发表于 2011-10-1 23:45:41

我觉得可以这么想：原题：OG 12 P52-15

选C： 2.3.5.7.11.13.17.19---2*5=10 3*7~20 11~10 13~15 17~15 19~20
10*20*10*225*20~10*20*10*200*20=8*10^6~10^7

the product of all the prime numbers less than 20 is closest to which of the follwing powers of 10?
A.10^9
B.10^8
C.10^7
D.10^6
E.10^5

-- by 会员 cyx1106 (2011/10/1 19:55:23)

-- by 会员 jingnnee (2011/10/1 22:04:43)

谢谢！！~

所属分类: GMAT考试