这道题怎么做啊?z这个类型的老是做错

葛佳 · 发表于 2010-6-1 21:02:47

A vending mashine is designed to dispense 8 ounce do coffee into a cup. After a test that the number of ounces of coffees of 1.000 cups dispended by the vending machine, the 12 listed anountes; in ounce were selected from the data , if the 1.000 recored anounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounce how many of the 12 listed amounts are within 1.5 standard deviation of mean.
7.51   8.22   7..86   8.36
8.09   7.83   8.30   8.01
7.73   8.25   7.96   8.53

葛佳 · 发表于 2010-6-1 21:05:23

If n is an integer between 10 and 99 is n<80?
(1) the sum of the two digit of n is a prime number
(2) each of two digits of n is a prime number

葛佳 · 发表于 2010-6-1 21:07:16

What is the average of eleven consecutive integers?
(1) the average of the first 9 integers is 7
(2) the average of the last 9 integers is 9

葛佳 · 发表于 2010-6-1 21:13:47

What is the average of eleven consecutive integers?
(1)   the average of the first 9 integers is 7
(2)   the average of the last 9 integers is 9
In triangle ⊿ABC what is length of BC?
(1)   line segment AD has lengthen 6
(2)    x=36

葛佳 · 发表于 2010-6-1 21:16:26

What is value of 5x平方 +4x — 1
（1） x( x+2)=0
（2） x=0
为什么（1）不可以啊？

西安泡馍 · 发表于 2010-6-1 21:20:12

试着回答
第一题：就是找出在 (8.1-1.5*0.3, 8.1+1.5*0.3)的读书的个数
第2踢： 1）加入数字是85或者34，错， 2）我觉得充分最大就是77了
第三体：我觉得都行吧。。。。

葛佳 · 发表于 2010-6-1 21:28:16

试着回答
第一题：就是找出在 (8.1-1.5*0.3, 8.1+1.5*0.3)的读书的个数
第2踢： 1）加入数字是85或者34，错， 2）我觉得充分最大就是77了
第三体：我觉得都行吧。。。。

-- by 会员西安泡馍 (2010/6/1 21:20:12)

1.5 standard deviation *0.3 哦明白了这一类的题目都是这样的 mean—+ x1 standard deviation * x2
第三个只有第二个是对的
我也是都选的错了

葛佳 · 发表于 2010-6-1 21:30:02

If n is an integer between 10 and 99 is n<80?
(1) the sum of the two digit of n is a prime number
(2) each of two digits of n is a prime number 、

怎么做？这类题也是不是很会做的

葛佳 · 发表于 2010-6-1 21:53:54

What is value of 5x平方 +4x — 1
（1） x( x+2)=0
（2） x=0
为什么（1）不可以啊？

-- by 会员葛佳 (2010/6/1 21:16:26)

因为求不出唯一的解

afei0128 · 发表于 2010-6-1 22:37:04

If n is an integer between 10 and 99 is n<80?
(1) the sum of the two digit of n is a prime number
(2) each of two digits of n is a prime number 、

怎么做？这类题也是不是很会做的

-- by 会员葛佳 (2010/6/1 21:30:02)

我认为选B

1)举例法。n=85和n=76都符合条件。但显然不能判定是否大于80

2)个位和十位都必须是质数。显然十位只能为2,3,5,7.所以必然小于80

请指教，谢谢

这道题怎么做啊?z这个类型的老是做错

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