GWD-7-16,30

songyang0121

求助~呵呵

16:if k is a positive integer,what is the remainder when 2的k次方 is devided by 10?

(1)k is devisible by 10

(2)k is devisible by 4

(b)

30:there are 8 books ,2 are p and 6 are h,how many possible selections of 4 books at least one p?

(50) 我怎么觉得应该是55呢？

另还有一道

if d 等于1除以（2的3次方乘以5的7次方）is expressed as a terminating decimal,how many nonzero digits will d have?

(2)我认为只有8一个非零的啊

哎 做og 的时候以为数学很简单……

erikajin

第一题 2的n次方尾数以 2 4 8 6 循环， 如果k是4的整倍数， 则明显余数是0

而k是10的倍数不能确定

第二题 我同意你的答案 呼唤大家帮忙看看

第三题 相当于 1 除以10的3次方乘以5的4次方 那么就是1除以625了nonzero digits 是1和6

songyang0121

THX~haha

tigerflying

the second one should be 55.

the third one: 1/(2^3*5^7)=2^4/(2^7*5^7)=16*10^(-7), so the nonzero number is 1 and 6.