标题: just can't figure it out...:( [打印本页] 作者: lisaislisa 时间: 2002-12-3 17:05 标题: just can't figure it out...:(
from XDF GMATCAT [em15]
1. three-digit number , if the first digit is a prime number and the last number is also a prime number , how many numbers accord with the pattern ?
AN 160
[em15][em15][em15][em15][em15][em15][em15]
2 the formula for diagnals and sides for polygon is d=n(n-3)
if the diagnals is twice as many as the sides , what side there will be
An is 7
but mine An is 5
as 2n=d ,d=n(n-3) => n=5
I failed to find out the flaws from my An ,although I am afraid it's just a easy pro....[em17]
THaNKs to All [em19]
[em19]作者: freedim 时间: 2002-12-3 22:51
QUE1: 0-9中质数2，3，5，7 所以C4^1*C10^1*C4^1=160
QUE2; I agree with yours作者: BATI巴蒂 时间: 2002-12-3 22:56
1. 10以内的质数只有4个:2,3,5,7.
则有: 4*10*4=160
2. 答案为5.作者: lisaislisa 时间: 2002-12-3 23:12
so 1 is not prime number ?...
humble quesiton , isn't it ...
anyway , just got the news of succeed in exposition bidding ..
so excited !!!
grant all of you good luck ^^作者: BATI巴蒂 时间: 2002-12-3 23:18
